Autodesk Moldflow Insight 2010 Std2 Practice

Autodesk Moldflow Insight Standard 2

PRACTICEFOR RELEASE 2010

February 2009

© 2009 Autodesk, Inc. All rights reserved.

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Disclaimer

THIS PUBLICATION AND THE INFORMATION CONTAINED HEREIN IS MADE AVAILABLE BY AUTODESK, INC. "AS IS." AUTODESK, INC. DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE REGARDING THESE MATERIALS.

About this manual

The Autodesk Moldflow Insight Standard 2, Practice manual is designed with the new Moldflow user in mind. In creating this manual, our goal was to introduce you to some basic plastic flow and design principles in addition to skills needed to translate, analyze and interpret models.

There is a significant amount of information in this manual, more information than can be absorbed during the class. This manual should be useful as a handy desk reference when back in the office.

Using this manual

This manual is separated into several chapters and appendices. Each of the chapters covers a specific topic and includes the following sections:

Aim

Describes the learning objectives of the chapter.

Why Do It

Outlines the reasons for following the prescribed guidance, suggestions, and methodology within the chapter.

Overview

A complete outline of what will be covered within the chapter.

Practice

This section contains hands-on exercises used to reinforce what was learned. The practice section guides the user through the steps necessary to complete a project.

v

Formatting used in this manual

Tasks

: To perform a step on the computer

1. When the Task icon is shown, below it is a list of numbered steps to complete the task.

1.1. Tasks can have a sub-step,

• A bulleted list provides information on a step, or a non-sequential actions to be done,

A second level bulleted list to provide information on a sub-step.

2. A task is used in the practice section of a chapter to indicate steps to be done on the computer.

Bulleted lists

• A bulleted list contains a number of items that have no particular order.

• It does not represent a list of steps that have to be followed in sequence.

Ruled paragraph

Tip

Note

Text from a computer screen is shown between ruled lines.

/ A tip is a useful piece of information that is normally associated with a task or procedure. Something that can be done to make a task easier or more efficient.

3 A note is generally used to highlight some background or theoretical information.

vi

Training files setup

The files required for the Autodesk Moldflow Insight Standard 2 class are organized into several folders. Each folder has the files necessary for one chapter. The table below shows the required folders, translation and study files, and results necessary for the class. In each folder, there will be a *.mpi file with the same name as the folder. The mpi file is the database of the Project pane in Synergy. All the results that need to be run will be provided in class. However if for some reason the results are not available, they can be obtained by analyzing the necessary studies.

Table 1: Files Required for the Autodesk Moldflow Insight Standard 2 Class

Folder name Files Needed Results neededDatabase_Management Cover.sdy

Mat1804.21000.udbMat1805.21000.udb

DOE Cap.sdyPlate.sdy

Fill + Pack + DOE on Cap

Family_Tools Box.sdyLid.sdy

Insert Overmolding Insert DDConnector DDConnector 3D Pre-Run

Fill + Pack on Connector 3D Pre-Run

Multiple_Gates door_panel.sdyDrawer.sdy

Packing_Optimization SC Fill.sdySC Flat Prof.sdySC3 Fill.sdySC3 Flat Prof.sdy

NoneCoolNoneCool

Projects Boot.igsCap.igsChange_tray.igsCover.igsDrawer.igsDustpan.igsGrabit.igsLight_holder.igePaper_Holder.igsphone.igsreel.igsSnap_Cover.igs

vii

Two-Shot Box DDWindow DDBox & Window Pre-RunMF Logo DDMF Back DDMF Back & Logo Pre-RunMF Back & Logo Test match

Fill + Pack + Overmolding Fill +Pack onConnector 3D Pre-Run,MF Back & Logo Pre-Run,MF Back & Logo Test match

Table 1: Files Required for the Autodesk Moldflow Insight Standard 2 Class

Folder name Files Needed Results needed

viii

ContentsAbout this manual ........................................................................................................................vUsing this manual .........................................................................................................................vFormatting used in this manual .................................................................................................viTraining files setup .....................................................................................................................vii

CHAPTER 1Database Management ........................................................................... 1

Practice - Database Management ............................................................................................... 3Setup ....................................................................................................................................3Creating a personal database ............................................................................................3Edit a material property ....................................................................................................5Read in a Personal Database material into a study .......................................................5Competency check - Database Management ................................................................ 7Evaluation Sheet - Database Management .................................................................... 9

CHAPTER 2Family Tools .......................................................................................... 11

Practice - Family Tools .............................................................................................................. 13Design criteria ..................................................................................................................13Project setup .....................................................................................................................13Finding molding conditions and optimizing the parts ..............................................14Building the family tool model ......................................................................................19Analyzing the tool ...........................................................................................................21Competency check - Family Tools ............................................................................... 25Evaluation Sheet - Family Tools ................................................................................... 27

CHAPTER 3Multiple Gates ........................................................................................ 29

Practice - Multiple Gates ........................................................................................................... 31Drawer Model .................................................................................................................. 33Door Panel ....................................................................................................................... 45Competency check - Multiple Gates ............................................................................ 59Evaluation Sheet - Multiple Gates ................................................................................ 61

CHAPTER 4Packing Optimization ............................................................................ 63

Practice - Packing Optimization............................................................................................... 65Snap cover with a Dual Domain mesh ........................................................................ 67Snap cover with a 3D mesh ........................................................................................... 85Competency check - Packing Optimization............................................................. 101Evaluation Sheet - Packing Optimization................................................................. 103

ix

CHAPTER 5Part Insert Overmolding ......................................................................105

Practice - Part insert overmolding......................................................................................... 107Connector ...................................................................................................................... 109

CHAPTER 6Two-Shot Sequential Overmolding ....................................................127

Practice - Two-Shot Sequential Overmolding..................................................................... 129Box with window.......................................................................................................... 131Moldflow logo............................................................................................................... 139

CHAPTER 7Design of Experiments (DOE) Analysis .............................................155

Practice - Design of Experiments (DOE) Analysis............................................................ 157Plate ................................................................................................................................ 158Reviewing the results of the cap ................................................................................ 160Answers.......................................................................................................................... 164Competency check - DOE ......................................................................................... 165Evaluation Sheet - DOE ............................................................................................. 167

CHAPTER 8Projects .................................................................................................169

Finding a gate location on a boot part ..................................................................................171Optimize the 8-cavity tool for cap .........................................................................................172Determine gate location and molding conditions for a change tray .................................174Find the gate location and size the runner system for a cover ..........................................176Determine gate locations for a chest of drawers .................................................................178Finding a gate location for a dustpan ....................................................................................179Determine type of tool and gate location for the Grab-it model ......................................180Determine the gate location for a light holder .....................................................................181Determine the gate location for the paper holder model to minimize weld lines ..........182Find a gate location and process settings for the phone housing model .........................183Find a gate location and size the manifold for the reel model ..........................................184Optimize a 4-cavity tool for the Snap Cover model ...........................................................186Find gate locations and balance runners for the door panel model .................................188What You’ve Learned ..............................................................................................................189

Index ............................................................................191

x

CHAPTER 1

Database Management

Aim

The aim of this chapter is to create or edit databases.

Why do it

Customizing databases allows you to create material that is not in standard databases, or to change the values of something that is in a standard database. Most of the time this is a thermoplastic material, but it could also be geometry/mesh properties. You can even edit the defaults for all parameters that are used within the program. Editing databases can be done so you can run an analysis on a custom material, or in the case of geometry databases, create the standard geometry you use.

Overview

There are several methods available for creating, editing and using databases. In this chapter, you will look at the methods available for working with the databases. The method used will depend on what you are editing and why. Many times you may start by copying an existing material or database record and then modify it. You may also create a new database and enter all the information manually.

Database Management 1

2 Chapter 1

Practice - Database Management

Below are 3 short examples of working with personal databases

Setup

To open a project

1. Click (File Open Project) and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Database_Management.

2. Double click the project file Database_Management.mpi.

3. Click File Preferences.

3.1. Ensure the active units are set to metric units.

To open the cover model

1. Click on the file Cover. sdy, and click Open.

2. Rotate the model around to review the geometry.

Creating a personal database

To create a personal material database

1. Click Tools New Personal Database.

2. Ensure the Category field is set to Material in the drop-down menu, See Figure 1.

3. Select the Property Type field to Thermoplastics Material.

4. Name your personal database by clicking on and typing mymatdb.

5. Click the Save button.

6. Click the OK button.

• The Properties dialog opens as shown in Figure 2.

To read in existing UDB databases

1. Click button to access all other thermoplastic databases.

• The standard database is opened automatically.

2. Click to the right of the database name field.

2.1. Navigate to the Database management folder.

This is the folder in which Synergy is open.

Practice - Database Management 3

3. Click on the file mat1804.21000.udb then click the open button.

• The contents of this database should now be in the lower half of the properties dialog.

4. Highlight the material in the mat1804.21000.udb database.

5. Click the button twice to transfer the material to your personal database in the top half of the dialog making two copies.

6. Click the icon again and read in mat1805.2100.udb.

• Copy that material to the personal database.

Figure 1: New database dialog

/ To select more than one entry, hold down the Ctrl key while clicking on multiple entries.

/ If you have read in a database and don’t see any materials or not all of them, open the search criteria dialog and clear the filters.

3 The file mat1804.21000.udb is the type of file you would get from Moldflow Plastics Labs when you had a material tested.

4 Chapter 1

Figure 2: Properties dialog

Edit a material property

In the mymatdb database, there should be two copies of the material Styron 693.

To edit a material

1. Click to highlight the second copy of the Styron 693.

2. Click the button.

3. Click on the Recommended Processing tab.

4. Change the Mold surface temperature from 42.5ºC to 50ºC

5. Change the Melt temperature from 225ºC to 250ºC.

6. Change the Name to Styron 693: Changed Mold and Melt.

7. Click on the Description tab.

8. Change the Trade name to Styron 693mod.

9. Click OK.

10. Click OK on the Property’s dialog to close the dialog and finish the editing.

Read in a Personal Database material into a study

To find the material

1. If the cover study is not open, click on the icon in the project view to open it.

2. Double-click (Materials) to select a material.

3 The Name field in the thermoplastic material dialog is the description field from a search listing. For the material you just entered, the description is Styron 693: Changed Mold and Melt.


3. In the Manufacturer field, type my. This should find your database Mymatdb.

4. Tab to the Trade name field.

5. Select Styron 693.

6. Click OK to select the material.

To check the processing conditions

1. Double-click (Process Settings).

2. Check the value of the Mold surface temperature and Melt temperature.

• They should be 42.5ºC and 225ºC respectively. These are the original values.

3. Click Cancel to close the Process Settings dialog.

To read in the second Styron

4. Double-click (Materials) to select a material.

5. In the Manufacturer field, type my. This should find your database Mymatdb

6. Tab to the Trade name field.

7. Select Styron 693mod.

8. Click OK to select the material.

To check the processing conditions

1. Double-click (Process Settings).

2. Check the value of the Mold surface temperature and Melt temperature.

• They should be 50ºC and 250ºC respectively. These are the modified values.

3. Click Cancel to close the Process Settings dialog.

6 Chapter 1

Competency check - Database Management

1. What would be the procedure necessary to create a database for standard edge and tunnel gates your company uses?


8 Chapter 1

Evaluation Sheet - Database Management

1. What would be the procedure necessary to create a database for standard edge and tunnel gates your company uses?

1. Click Tools New personal database.

2. Enter a database name such as Mygates.

3. Select the category Mesh properties.

4. Select the property type Cold gate.

5. Click the Databases button to open the standard cold gate database. (Optional).

6. Copy an edge and tunnel gate (subgate) that are close to the correct properties. (Optional).

7. Edit the properties as necessary.

8. Exit the dialog.


10 Chapter 1

CHAPTER 2

Family Tools

Aim

In this chapter you will create a family tool and size the runners, so that both cavities fill in the same amount of time and pressure.

Why do it

The purpose of a family tool is to reduce the number of molds needed by combining multiple parts (two or more) into a single mold. Typically, the parts will be assembled together. The reasoning behind this is usually due to cost reduction measures.

Although it is possible to place two or more different parts into the same mold, it will cause a problem with unbalanced filling. Therefore, it is necessary to balance the filling of the multiple cavities via the runner system.

Overview

This chapter uses midplane models in the practice. The runner balancing procedure being discussed in this chapter can be applied to both Dual Domain and midplane models. Family tools can be analyzed in 3D but their runners can't be balanced in the methods discussed in this chapter. A Dual Domain version of the models can be created for the purpose of balancing the runners then verified in the 3D model.

In this practice, you will optimize process settings for a family tool, and build and balance its runner system.

The main challenge in using family tools is that the parts usually have different volumes and require different pressures to fill. This chapter demonstrates how to overcome this challenge by following these steps:

1. Use the Molding Window analysis to find a set of processing conditions that will work for both parts.

2. Run a Fill analysis for both parts to verify that the process settings selected work, optimize the part filling, and find the part volumes.

3. Add the models together and create the runner system for the new model.

4. Change to flow rate control, using the combined part volumes, and run a Fill analysis.

Family Tools 11

5. Size the runners to achieve the desired balance using flow rate and the runner balancing.

3 For some larger family tools where each part has multiple gates, it may be more efficient to size the runners manually.

12 Chapter 2

Practice - Family Tools

In this section, you will analyze the Box and Lid and balance the runner system for the two cavity family tool.

Design criteria

Determine the molding conditions that will work for both parts to mold high quality parts. Build and size a runner system so both parts fill at the same time. The mold will be a 3-plate tool.

Project setup

To open a project

1. Click (File Open Project) and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Family_Tools.

2. Double-click the project file Family_Tools.mpi.



3.2. Click on the Directories tab.

3.3. Ensure the Default to project directory box is checked.

• By having the box checked, the import dialog will open in the project directory.

The next task loads a workspace customized for training classes. Primarily, it introduces you to the toolbars. This is an optional task.

To load a workspace for training (optional)

1. Click Tools Workspace Open.

2. Select Other... in the Type field.

3. Navigate to the Workspaces folder containing the project folders for this class and click OK.

• For example My AMI 2010 Projects\AMI Standard 1\Workspaces.

Practice - Family Tools 13

4. Select the workspace file Training Workspace and click Open.

• The workspace will load. Primarily, it opens a series of toolbars and leaves them undocked so you can see the name of the toolbars. Toolbars with the word Custom in the name are not standard toolbars but were created as an example of tool bars that can be made. The toolbars include:

5. Click and drag the toolbars and dock them where you would like them.

• Typically the Viewer toolbar is docked vertically between the Tasks panel and the display area. The rest are typically docked below the menu bar.

To review the model

1. Open both models.

2. Investigate the model geometry using the model manipulation tools.

Finding molding conditions and optimizing the parts

The molding conditions will be found by using the molding window analysis. The box and lid will be analyzed separately, then the Molding window results will be compared to find the same conditions that work for both parts. The molding window will be done twice for both parts. The first time with default options. From this, the injection time range will be determined. Then, a molding window analysis will be run with specified ranges for mold and melt temperatures, and injection time. The preferred and feasible molding windows will also be defined.

The part geometries are very simple for these parts so part optimization is just a matter of running a fill analysis to make sure the molding conditions are good. For more complex parts, optimization may involve solving any type of flow problem that is found.

To run a molding window analyses on the box with default conditions

1. Activate the Box study.

2. Click (File Save study as) and enter Box MW1.

3. Click (Analysis Sequence) and select Molding Window.

4. Click (Select material) and find BASF, Luran 368 R.

• Standard. • Viewer. • Animation

• Precision View • Viewpoint. • Selection

• Scaling. • Custom General. • Custom Results.

• Custom Mesh Diag. • Custom Mesh Tools. • Custom Locking.

3 To get back to the default layout, click Tools Workspace Open and in the Moldflow Insight workspaces type, select Defaults.

14 Chapter 2

5. Click (Start Analysis) to run the Molding Window analysis.

To view the results for the box

1. Open the Analysis Log and record in Table 1, the range of mold and melt temperatures analyzed.

2. Click Pressure drop, maximum (molding window):XY Plot to display it.

3. Click (Results Plot Properties).

4. Move the Injection time slider to find the minimum and maximum time plotted.

5. Record the minimum and maximum times in Table 1.

6. Check the Injection time box and move the sliders to ensure the pressure is not too high.

7. Click Close to exit the Explore Solution Space dialog.

To run a molding window analyses on the lid with default conditions

1. Activate the Lid study.

2. Click (File Save study as) and enter Lid MW1.

3. Click (Analysis Sequence) and select Molding Window.

4. Click (Select material) and find BASF, Luran 368 R.

5. Click (Start Analysis) to run the Molding Window analysis.

To view the results for the Lid

1. Click Pressure drop, maximum (molding window):XY Plot to display it.


3. Move the Injection time slider to find the minimum and maximum time plotted.

4. Record the minimum and maximum times in Table 1.

5. Compare the injection time ranges and determine the minimum and maximum common to both studies.

6. Record the values in Table 1.


To run a molding window analysis on the box with specified parameters

1. Activate the Box MW1 study.

2. Click (File Save Study).

3. Click (File Save study as) and enter Box MW2.

4. Double-click (Process Settings) in the Study Tasks pane.

4.1. Click the Edit button in the Injection molding machine frame.

4.2. Click the Hydraulic Unit tab.

4.3. Set the maximum machine injection pressure to 140 MPa.

4.4. Click OK to exit the dialog.

5. Set the Mold temperature range to analyze to Specified, and enter the range recorded in Table 1.

6. Set the Melt temperature range to analyze to Specified, and enter the range recorded in Table 1.

7. Set the Injection time range to analyze to Specified, and enter the range recorded in Table 1.

8. Click the Advanced options button.

8.1. Set the injection pressure factor to 0.8 in the Feasible molding window.

8.2. Set the injection pressure factor to 0.5 in the Preferred molding window.

8.3. Set the Flow front temp. Maximum drop to 20ºC.

8.4. Set the Flow front temp. rise limit to 2ºC

8.5. Click OK to exit advanced options.

8.6. Click OK to exit the Process Settings Wizard.


10. Click (Start Analysis).

Table 1: Molding conditions notes

Parameter ValueBox Mold temperature range analyzedBox Melt temperature range analyzedBox Injection time range analyzedLid Injection time range analyzedCombined injection time range to analyze

16 Chapter 2

To run a molding window analysis for the lid

1. Repeat the steps in the previous task for the lid model.

To find one set of process conditions that work for both parts

1. Ensure that both the Box MW2 and Lid MW2 studies are open.

• Close any additional windows.

2. Click Window Tile Vertically.

3. Click (View Lock All plots) so results in both studies can be manipulated at the same time.

4. Click the Molding window:2D Slice Plot in the study tasks list.

5. Click (Results Plot Properties) for the molding window plot.

5.1. Set the cut axis to Mold Temperature.

5.2. Set the Cut position to 40ºC.

A 40ºC mold temperature is a reasonable temperature for both parts.

5.3. Click OK.

6. Examine the molding window plots for both the box and lid.

• The X-axis for melt temperature is the same.

• The Y-axis for injection time is the same because the time range was specified in the analysis. If the analysis was left on automatic, the time range would be different. Getting the same range analyzed is the reason the molding window was run twice.

• The green area represents preferred conditions for the part. The size of the preferred windows is different, and don’t overlap much with the time range.

7. Click (Examine Results) at 240ºC, as this is a mid range temperature for the box.

• Find 0.7 seconds on both parts. Notice how this time is on the fast side for the box, and on the slow side for the lid, but it works for both.

The molding conditions to be used for both parts are:

To run a fill analysis on the box

1. Ensure the Box MW2 study open and active.

2. Double-click (Analysis Set Analysis Sequence) and select Fill.

3. Click Create a Copy, when prompted.

Mold Temperature 40 ºCMelt Temperature 240ºCInjection Time 0.7 sec.


4. Name the new study Box Fill.

5. Double-click (Process Settings Wizard) and enter the following conditions.

6. Double-click (Start Analysis).

To run a fill analysis on the lid

1. Ensure the Lid MW2 study open and active.

2. Double-click (Analysis Set Analysis Sequence) and select Fill.

3. Click Create a Copy, when prompted.

4. Name the new study Lid Fill.

5. Double-click (Process Settings Wizard) and enter the following conditions.


To review results

1. Ensure both the Box Fill and Lid Fill studies are open and all other studies are closed.

2. Click Windows Tile Vertically.

3. Click (View Lock All plots).

• Results in both studies will be displayed and manipulated at the same time.

4. Rotate, pan, or zoom each part as necessary to get a good view.

5. Plot the following results:

• Fill time.

• Pressure at V/P switchover.

• Bulk temperature.

5.1. Animate the results as necessary.

5.2. Ensure all the results are acceptable.

Mold Temperature 60 ºCMelt Temperature 245ºCInjection Time. 0.7 sec.

Mold Temperature 60 ºCMelt Temperature 245ºCInjection Time. 0.7 sec.

18 Chapter 2

To determine the volume of the box and lid

1. Click Box Fill to activate it.

2. Click Mesh Mesh Statistics.

3. Record box volume in Table 2.

4. Click Lid Fill to activate it.

5. Click Mesh Mesh Statistics.

6. Record Lid volume in Table 2.

7. Add the part volumes together and record it in Table 2.

Building the family tool model

To add the box and lid models together

1. Activate the Box Fill study.

2. Click (File Save study as).

2.1. Enter the name Box Lid.

3. Click (File Add).

4. Select the study Lid Fill and click Open.

Table 2: Volumes

Component VolumeBox Lid Sum of parts

3 The Box and Lid models were imported into Synergy in tool position. When the Lid was added to the Box model they were automatically in the correct location.

/ It is best to put the parts of the family mold in tool position before they are added together.


To build the runner system

1. Ensure the Box Lid study is open and active.

2. Click Modeling Runner System Wizard.

2.1. Create the runner system for the box and lid, using the dimensions shown in Figure 3.

2.2. Create the runners with a circular cross section that is equal to the height of the runner.

The runner balance analysis only sizes round runners.

The runners can be converted to trapezoidal after the balance.

Figure 3: Runner drawing

The drops in the runner system are set to unconstrained. Tapered features of the feed system should not be changed during a runner balance. To prevent the change, the drops are going to be changed from a runner to gate property.

Constraining the dropsThe drops between the part and main runner are tapered, and should not be sized during the balance. The Runner creation wizard created the drops with a cold runner property. If nothing was changed, the drops would be sized during the balance. To prevent the drops from being sized during the balanced one of two things can be done:

• The runner sizes can be fixed to their current size.

• The runner property can be changed to a gate property.

The runner balance algorithm will not size properties of a Sprue or Gate. Only runners are changed. For this example, the property of the drops will be changed to Gate.

20 Chapter 2

To fix the drop dimensions

1. Select all the elements in either one of the tapered drops, as shown in Figure 4.

2. Right-Click and select Change Property type from the context menu.

3. Select Cold gate on the Change Property Type To dialog.

4. Click OK twice accept the change.

5. Repeat the process for the other drop.

Figure 4: Selecting elements to change the properties

Analyzing the tool

A flow rate should be used as the filling control. This will ensure the parts will fill in the time determined as optimum.

To calculate the flow rate

1. Recall the total flow rate from both cavities that you have recorded in Table 2.

2. Divide this by the injection time used to fill the parts, which is 0.7 seconds.

3. Record the flow rate below.

To run a Flow analysis

1. Ensure the Box Lid study is open.

2. Double-click (Process Settings Wizard).

3. Set Filling Control to Flow Rate.

4. Enter the flow rate you calculated above.

5. Set the Fill/Pack switch-over to by % volume filled at 100%.

6. Set the Pack/holding control Profile Settings to % Filling pressure to 100%.

• This study will be duplicated for runner balancing, which works better when the pressure does not drop after the switch-over. Once the runners are balanced, you may set the switch-over to the desired value.

Band Select

Flow Rate = cc/sec.


7. Click OK twice.


To review results to determine balance inputs

1. Plot Fill Time.

2. Click (Animate result).

3. Step the animation from the start of fill until the Lid is just full.

• Note how much there is left to fill on the Box.

4. Plot the Pressure.

• Pressure is very sensitive to the runner balance. Notice how the pressure of the lid is very high compared to the box.

5. Plot the Pressure at injection location.

• This is an XY plot of the pressure gradient at the injection location.

• The pressure spike at about 0.7 seconds corresponds to the lid filling and the box has yet to fill out. See Figure 5.

• In this case, the balance pressure that will be used is 58 MPa which is slightly above the pressure at the end of fill.

Figure 5: Pressure XY graph at the injection location

To balance the runners

1. Double-click the Analysis Sequence icon in the Study Tasks pane.

2. Select Runner Balance.

3. Click OK.

• If Runner balance is not in the list, click the More button and choose runner balance from the full list of analysis sequences.

/ The higher the balance pressure, the smaller the runner diameters will be which will save material. However if the runner diameters are too small, the parts with the small runner may not pack out properly.

22 Chapter 2

4. Double-click the Process Settings icon in the Study Tasks pane.

4.1. Ensure the filling parameters are correct.

4.2. Click Next.

4.3. Set the target pressure to 60 MPa.

4.4. Click Advanced Options.

4.5. Set the Mill Tolerance to 0.1 mm

4.6. Click OK.

4.7. Click Finish.

5. Double-click (Continue analysis).

Review the results

To view the Analysis Log results

1. Open the Analysis Log if necessary.

2. Watch the analysis progress or review it when the analysis is done.

3. Review the iteration table.

• The last iteration should be below all three tolerances.

• If it reached the iteration limit, one more analysis is run with the iteration that had the lowest time imbalance.

To review volume change

1. Click on the Volume change result in the Box Lid study.

2. Notice the distribution of volume change.

• Only the runners have results, because this was the only thing that could change.

• The percent change will be zero if the runner size is fixed.

• A negative volume change indicates the runner got smaller, and is generally preferred.

• A positive volume change indicates the runner has gotten larger and in generally an indication that the balance (target) pressure is too low.

To view the thickness changes

1. Double-click on the Box Lid (Runner Balance) study to open it.

2. Rotate the model as necessary to see the runners and parts. A good rotation is -70 -25 -10.


3. Plot the thickness diagnostic.

3.1. Click the Tools tab.

3.2. Click (Mesh Diagnostic).

3.3. Select Thickness Diagnostic.

3.4. Click Show.

4. Click (Examine result).

5. Click on the runners.

• Notice how both are less than 6 mm, (the original sizes), hence the negative volume in the volume change plot.

To plot fill time

1. Click the Fill time result.

2. Click (Animate).

• Notice how the flow fronts are very balanced compared to the first analysis.

To plot pressure

1. Click the Pressure at V/P switchover result.

• Notice how the Box fills last.


3. Click on the parting line of the lid.

• Notice that the pressure is just above zero, while there is a noticeable portion of the box not filled yet.

To review other results

1. Plot other results to see the influence of the balance.

2. If desired, tile the windows and lock the studies:

• Box Lid.

• Box Lid (Runner Balance).

3. Compare the filling results between the two analyses.

Finishing upIf the balance results are acceptable, possibly the runner dimensions can be rounded. Any changes in runner diameter from the optimum will influence the balance. If the sized runners are close to a standard size, rounding may be acceptable. Any rounding that is done should be validated using a Fill + Pack analysis to check the balance but also volumetric shrinkage.

24 Chapter 2

Competency check - Family Tools

1. What is the ideal scenario when creating family molds, with regards to part volume?

2. List the main steps to optimize a family mold

3. How does the procedure to analyze family molds differ from analyzing multi-cavity tools?


26 Chapter 2

Evaluation Sheet - Family Tools

1. What is the ideal scenario when creating family molds, with regards to part volume?

• The volume of the parts in the family tool should be close together. When one part is many times larger than another, the balance becomes difficult and the molding window gets small.

2. List the main steps to optimize a family mold

• Moldflow recommends following the steps listed below:

1) Use the Molding Window analysis to find the same processing conditions that works for each one of the parts.

2) Run a Fill analysis to verify the process settings, optimize the part filling and find the volumes of the parts.

3) Add all the parts to one study file and create the runner system.

4) Balance the runners with the runner balance analysis, manually or a combination.

3. How does the procedure to analyze family molds differ from analyzing multi-cavity tools?

• There are multiple parts of different volumes and pressures to fill. There must be one set of processing conditions found that fills each one of the parts. When the variation in part size becomes large, the molding window may get quite small.


28 Chapter 2

CHAPTER 3

Multiple Gates

Aim

The aim of this chapter is to determine the optimum number and location of gates to make the part fill evenly and with an acceptable pressure.

Why do it

Two or more gates per cavity are sometimes required for large products where the flow distances from a single gate would be too long, or one gate cannot produce a balanced filling pattern. Finally multiple gates can be used to move weld lines.

Overview

In this chapter, you will look at the issues involved with using multiple gates on parts. There are two types of problems related to multiple gates: symmetrical and non-symmetrical part geometries. With a symmetrical gating location, the flow length and pressure drop and volume from each gate is about the same. With non-symmetric gate locations, the flow length, pressure and flow length is not the same. In both cases, the runners need to be balanced by changing the runner diameter to provide the correct volume to each gate so the filling pattern will be balanced.

This chapter will use the Molding Window analysis and the fast analysis as an aid for solving the problem. In this chapter you will also learn how to work with clamp tonnage.

Multiple Gates 29

30 Chapter 3

Practice - Multiple Gates

This chapter has several models that are used for practice and are described below. Proceed with the model of your choice. Do the others as time permits.

Table 3: Models used for molding window analysis

Description ModelDrawer: starts on page 33

The drawer model, or chest of drawers, has three gates on the front face of the part. The gate locations are fixed. The main objective is to balance the hot runners to fill the part with a balanced filling pattern.

Door panel: starts on page 45The door panel will require multiple gates. You must determine the gate locations and construct and balance the runners. You will have a clamp tonnage limitation for this part as well.

Practice - Multiple Gates 31

32 Chapter 3

Drawer Model

Design criteriaThe drawer will be made with a 2-plate tool using a hot runner system. Figure 6 indicates the position of the gates. The material is a high-density polyethylene. You will determine the optimum processing conditions, size, and balance the hot drops accordingly.

Figure 6: Drawer with injection locations

For the drawer model, you will perform the following:

• Run a molding window analysis with the provided gate locations.

• Run a filling analysis at the optimum processing conditions.

• Review filling results.

• Create a hot runner system using the runner creation wizard.

• Run a fill analysis with the runners.

• Evaluate flow balance.

• Change drop diameters to improve the balance as necessary.

• Re-run and review results.

Project setup

To open a project

1. Click (File Open Project) and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Multiple_Gates.

2. Double click the project file Multiple_Gates.mpi.







To review the model

1. Open the model Drawer.


3. Turn on the default layer to see the injection locations.

Determine molding conditions

To analyze the molding window

1. Double-click (Analysis Set Analysis Sequence) and select Molding Window.

2. Select the material BASF, Polystyrol 165 H.

3. Double click (Analysis Process Settings).


Click the Hydraulic Unit tab.

Set the maximum machine injection pressure to 140 MPa.

Click OK to exit the dialog.

3.2. Click the Advanced options button.

Set the Pressure factor to 0.8 in the Feasible molding window.

Set the Pressure factor to 0.5 in the Preferred molding window

Set the Flow front temp. Maximum drop to 20ºC.

Set the Flow front temp. Maximum rise to 2ºC.

Click OK to exit Advanced options.




6. Follow the General Interpretation Procedure below to interpret the results and determine your processing conditions.

7. Record the processing conditions you choose in Table 4 on page 40.

34 Chapter 3

Molding window general interpretation procedureThe procedure for looking at molding window results will vary, depending on the objectives of the analysis. The basic procedure is as follows:

1. View the Analysis Log.

1.1. Find the recommended processing conditions near the bottom of the Analysis Log, as shown in Figure 7.

1.2. Compare the recommended conditions of mold and melt temperature to the ranges near the top of the Analysis log.

The recommended conditions should preferably be near the middle of the ranges.

If not, this would indicate you might need to investigate choosing conditions other than the recommended conditions.

Figure 7: Molding window Analysis Log

Analysis commenced at Wed Jul 09 09:15:31 2008Analysis has detected a mesh change since initial mesh generation ... recalculating mesh match and thickness information Processing Dual Domain mesh...Computing match using the maximal-sphere algorithm... finished processing Dual Domain mesh Mold temperature range to analyze = Automatic from mold temperature = 80.0 C to mold temperature = 95.0 C Melt temperature range to analyze = Automatic from melt temperature = 270.0 C to melt temperature = 295.0 C Injection time range to analyze = Automatic Limits for calculation of feasible molding window Shear rate limit = Off Shear stress limit = Off Flow front temperature drop limit = Off Flow front temperature rise limit = Off Injection pressure limit factor = 0.80 Clamp force limit = Off Limits for calculation of preferred molding window Shear rate limit factor = 1.00 Shear stress limit factor = 1.00 Flow front temperature drop limit = 20.00 C Flow front temperature rise limit = 2.00 C Injection pressure limit factor = 0.50 Clamp force limit factor = 0.80Maximum Design Clamp Force 7000.22 tonneMaximum Design Injection Pressure : 180.00 MPaRecommended Mold Temperature : 91.67 CRecommended Melt Temperature : 295.00 CRecommended Injection Time : 0.4612 s Execution time Analysis commenced at Wed Jul 09 09:15:31 2008 Analysis completed at Wed Jul 09 09:15:35 2008 CPU time used 3.88 s


2. View the Molding window 2D Slice Plot.

• The molding window plot shows a 2D shaded graph. It uses mold temperature, melt temperature and injection time. Two of the 3 variables form the axis of the graph, the other is the Cut axis for the graph. The best cut axis is mold temperature. When the cut axis is mold temperature, the X-axis is melt temperature, and the Y-axis is injection time, as shown in Figure 8.

• The cut axis can be animated with (Add XY Curve). Hold the left mouse button down and drag the mouse up and down.

• The molding window plot will give you a sense for the size of the molding window. The plot uses 3 colors:

Green - represents an area that is within the preferred molding window.

Yellow - represents the size of the feasible molding window. This would mean that one of the parameters of the preferred window is outside the limit. More than likely it is a temperature limit.

Red indicates the pressure is higher than the factor set for the feasible molding window.

Figure 8: Molding window plot showing the size of the molding window

36 Chapter 3

2.1. Set the cut axis to Mold temperature in the plot properties.

2.2. Use (Add XY Curve) to animate the molding window plot. Determine how much the mold temperature influences the size of the molding window.

Generally, as the mold temperature goes up, the size of the molding window increases but typically not by much.

Most of the time the mold temperature specified in the analysis log file is near the high end of the range. If there is little change in the size of the molding window, a midrange mold temperature can be used.

2.3. Set the mold temperature cut axis value to the mold temperature you want to use.

2.4. Use (Examine result) on the molding window plot to find the injection time and melt temperature found in the analysis log.

Ideally, the chosen conditions are near the middle of a large preferred window. If not, use the examine result tool to find the melt temperature and injection time that are near the size of the molding window.

Decide on the mold temperature, melt temperature, and injection time that you want to use. These will be the optimum conditions. You will look at other results at these conditions to confirm you like the optimum conditions or if you would like to modify them.

3. Check the Pressure drop, maximum (molding window) XY Plot.

3.1. Set the X-axis to be injection time, using the plot properties, shown in Figure 9, slide the optimum mold and melt temperature to the values determined in the molding window plot.

3.2. Use the examine result tool to find the optimum injection time on the pressure curve.

This represents the pressure required for the optimum conditions. See Figure 10 on page 38.

3.3. Make sure the pressure is under the 70 MPa (10,000 psi) guideline, or about half the machine injection capacity. With the proper molding machine settings, and Advanced options settings, the green area of the zone plot will be under half of the machine’s pressure capacity

3 The molding window plot is most meaningful if the machine pressure capacity is known and the pressure factors for the feasible and preferred windows are set.


Figure 9: Molding window, explore solution space - plot properties

Figure 10: Pressure drop XY graph

4. Check the Temperature at flow front, minimum (molding window) XY Plot.

4.1. Set the X-axis to be injection time, using the plot properties slide the mold and melt temperature to the optimum conditions.

4.2. Use the examine results tool to find the optimum injection time.

The best injection time will be when the flow front temperature is about equal to the melt temperature.

38 Chapter 3

4.3. Use the examine results tool to find where the temperature is 0º C, 10º C. (18º F), and 20º C. (36º F) below the melt temperature. See Figure 11 on page 39

A 0º C drop in temperature defines the highest quality.

A 10º C (18º F) drop in temperature in most cases is a very acceptable amount of drop.

A 20º C (36º F) defines the limit of the preferred molding window, assuming it was set a maximum temperature drop of 20ºC (36ºF) in the advanced options.

Finding at what times these temperatures occur will give you another way to get a sense for the size of the molding window as the flow front temperature is generally the limiting factor in the molding window.

Figure 11: Minimum flow front temperature graph

5. Check the Maximum Shear Stress XY Plot.

5.1. Set the X-axis to be injection time, using the plot properties, and slide the mold and melt temperature to the new conditions.

5.2. Make sure the shear stress is below the material limit.

The lower the shear stress, the better.

Typically, the maximum shear stress plotted in this result will be significantly higher than the nominal shear stress in the part. If the shear stress is near or above the limit for this plot, you should concentrate on the shear stress result when you run a fill or pack analysis. You should find that the majority of the part has acceptable levels of stress and there may be some limited areas of high stress.

/ Up to four XY plots can be viewed and manipulated at the same time. Split the screen into 2 or 4 windows. Plot in each of the windows a different XY graph. For one of the graphs, open the plot properties. On the Explore Solution Space –XY Plot dialog, check the Lock all molding window XY plots in this study box. Now as you manipulate the sliders, all windows will update accordantly.


6. Check remaining plots.

6.1. Cooling time

The cooling time is viewed to see what effect processing conditions have on the cooling time. Mold temperature generally has the greatest influence so that should be the X axis.

6.2. Shear Rate

The shear rate will never be excessive in your part as a whole. There may be some very local areas where the shear rate approaches the limit. Plotting the shear rate from a molding window analysis will show you how the shear rate drops with the increase of the injection time.

The quality plot

The molding window analysis determines the recommended processing conditions, found in the analysis log, based on the set of conditions that has the highest quality. The quality is calculated using the parameters in the advanced options described earlier. The maximum quality possible is 1.0. Generally the maximum values for a given part are between 0.8 and 0.95. There will be many combinations of mold temperature, melt temperature, and injection time that will have quality values close to the recommended processing conditions. The Molding window plot easily shows this by the size of the green area. It is useful to view the quality plot to understand how the recommended conditions are picked, but the Molding window 2D Slice plot is the best plot to determine the optimum conditions and then use others to confirm the conditions.

To view the quality plot:

1. View the quality plot and set the X-axis of the graph to be injection time using the plot properties, as indicated in Figure 9 on page 38.

2. Adjust the mold and melt temperature sliders to the recommended mold and melt temperatures found in the Analysis Log.

• Normally, the data point with the highest quality is easy to visualize, as there is a sharp drop in quality from the maximum.

3. Use the Examine results tool to find the injection time of the data point with the highest quality. It will be the recommended injection time in the log file.

Run the first fill analysisThis is to verify the processing conditions used when the runner system is added.

Table 4: Drawer Processing Conditions used

Parameter ValueMold TemperatureMelt TemperatureInjection Time

40 Chapter 3

To run a filling analysis

1. Click (File Save Study as) and name the study Drawer fill.

2. Set the analysis sequence to Fill.

3. Enter the process settings that you determined from the molding window analysis.

4. Double-click (Start Analysis!).

To review the results

1. Plot the Fill time plot.

• Ensure the filling is balanced between the 3 gates.

2. Check the Pressure at V/P Switchover.

• Make sure the pressure is less than 70 MPa.

3. Check the Bulk Temperature.

• The range of temperatures should be less than 20º C.

4. Check the Shear stress at wall plot.

• Make sure the shear stress is not too high.

5. Check other plots as necessary.

6. Change some inputs and re-run the analysis if you are not satisfied with the results.

Create the hot runner system

To prepare for creating the runner system


2. Click (File Save Study as) and name the study DrawerRun1.

To create a hot runner

1. Click Modeling Runner System Wizard.

2. Select Center of gates, for the position of the sprue.

3. Click the I would like to use a hot runner system box.

4. Set the Top runner plane Z, for the location of the manifold per the drawing in Figure 13.

5. Set the sprue, runner and drop sizes per the drawing in Figure 13.

6. Set the gate size per the drawing in Figure 12.


Figure 12: Drawer gate detail

Figure 13: Drawer drawing

To run a fill analysis with the runners


2. Ensure the process settings are correct.



1. Plot Fill time.

1.1. Open Plot properties.

1.2. Change the Method to Contour.

42 Chapter 3

2. Decide if you think the filling is balanced enough.

3. Plot Pressure at V/P Switchover.

• Notice how the center of the sides has filled out, and the areas left to fill are on the outside corners. This is an indication that the balance could be better. The center is filling too fast. The top is also filling faster than the bottom.

The size of the top drop will be reduced to 7 mm and the center drop will be reduced to 5 mm to help create a better balance.

To revise the results


2. Click (File Save Study as) and name the study DrawerRun2.

3. Click (Bottom View)

4. Change the center drop.

4.1. Select all of the elements in the center drop. Refer to Figure 14.

4.2. Click (Edit Assign Property).

4.3. If prompted, select Beam element as the entity type and click OK.

4.4. Click New.

4.5. Select Hot runner to create a new hot runner property with:

A non-tapered circular shape.

A diameter of 5.0 mm.

Change the name to 5 mm drop.

5. Change the top drop. Refer to Figure 14.

5.1. Select the elements in the top drop.

5.2. Click (Edit Assign Property).

5.3. If prompted, select Beam element as the entity type and click OK.

5.4. Click New.

5.5. Select Hot runner to create a new hot runner property with:

5.6. Create a new hot runner property with:

A non-tapered circular shape.

A diameter of 7.0 mm.

Change the name to 7 mm drop.




Figure 14: Drawer drop locations


1. Plot the Fill time plot.

1.1. Click (Plot properties).

1.2. On the Methods tab, change the selection to Contour.

• Now you can see that the balance is better.

1.3. Open the DrawerRun1 study, and tile the results to compare them if desired.

2. Plot the Pressure at V/P Switchover.

• The Switchover is just early enough to see that the part is a bit more balanced.

SummaryReducing the center and top drops made the balance a bit better. To further improve the balance, the wall thickness on the part will need to be adjusted. The top of the part needs a flow deflector so the center of the top does not fill out so early. Also the bottom could be increased in thickness slightly to encourage flow in that direction.

Top drop Center drop Bottom drop

44 Chapter 3

Door Panel

Design CriteriaThe door panel is constructed with a 2-plate tool using a hot runner system. The tool is constructed with the underside of the part on the cavity side of the tool so it can be gated on that side. The tool will have cavity side ejection.

• The tool will go in a 1500 tonne press. The design clamp limit will be 1200 tonnes or 80% of the press’ capacity.

• The number and location of gates, plus the processing conditions are to be determined.

• There should be as few weld lines as possible.

• There must be no air traps in areas that are difficult or impossible to vent.

• The hot runner system must be sized and balanced so the filling pattern from the gate locations is balanced.

Figure 15: Door panel model

Figure 16: Door panel side view

PLUnderside


Analysis procedureFor the door panel model you will perform the following:

• Iterate between the gate location analysis and molding window analysis to determine the number and general location of the gates, in order to keep the fill pressure below 50% of the machine’s capacity.

• Run a filling analysis at the optimum processing conditions and gate locations determined.

• Review filling results.

• Revise the gate location(s) as necessary to get a good balanced filling pattern within the 1200 tonne clamp tonnage design limit.

• Create a hot runner system using the chosen gate locations.

• Run a fill analysis with the runners.

• Evaluate the filling.

• Change drop diameters in to improve balance as necessary.

• Re-run and review results.

Project setup

To open a project

1. Click (File Open Project) and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Multiple_Gates.

2. Double click the project file Multiple_Gates.mpi.






To review the model

1. Open the model Door Panel.


The clamp tonnage limit must be set for the initial study so all studies created after this point will have the correct clamp tonnage.

To set the clamp tonnage limit

1. Click the Process Setting Wizard.

2. Click the Advanced Options button.

3. Click the Edit button next to the Injection molding machine box.

46 Chapter 3

4. Click the Clamping Unit tab.

5. Enter 1200 in the Maximum machine clamp force field.

6. Ensure the Do not exceed maximum clamp force box is checked.

7. Click OK 3 times to get out of the dialogs.


Selecting gate locations and molding conditionsUsing the gate location analysis is a good way to get started for determining the gate location for the door panel. The gate location(s) for the door panel can be anywhere on the underside of the door panel.

To run an initial gate location analysis

1. Click (File Save Study as) as Door Panel Gate Loc 1.

2. Set the analysis sequence to Gate Location.

3. Select the material Kralastic SXB-367, an ABS from Sumitomo Chemical Company.

4. Click and ensure the Advanced gate locator is used and the number of gates is set to one.

5. Click OK to exit the wizard.

6. Click to run the analysis.

To view the gate location results

1. Click the Flow resistance indicator result.

• Notice how the gate location is near the arm rest. The analysis calculates the location to minimize the pressure, but you have no idea what this pressure is.

To run a molding window analysis at the chosen gate location

1. Right-click on the study Door Panel Gate Loc 1(Gate Location).

2. Select Rename and enter Door Panel Gate Loc 1 MW.

3. Double-click (Analysis Set Analysis Sequence) and select Molding Window.


4. Double click (Process Settings).


Click the Hydraulic Unit tab.

Set the maximum machine injection pressure to 140 MPa.

Click OK to exit the dialog.

4.2. Click the Advanced options button.

Set the Pressure factor to 0.8 in the Feasible molding window.

Set the Pressure factor to 0.5 in the Preferred molding window

Set the Flow front temp. Maximum drop to 20ºC.

Set the Flow front temp. Maximum rise to 2ºC.

Click OK to exit Advanced options.




7. Follow the Molding window general interpretation procedure on page 35 to interpret the results and determine your processing conditions.

• The molding window analysis does not output any results that indicate clamp force changes with processing conditions. However, if the pressure to fill is limited, so will the clamp force.

8. If you don’t like the molding window results, revise the gate location(s) and re-run the analysis. You can pick your own gate locations, or use the gate location analysis to help you pick more gates.

9. Record the processing conditions you select in Table 5.

Optimize the fillingNow that the gate location(s) and molding conditions have been found you need to run a fill analysis to see how the part actually fills and what the clamp force is.

/ In extreme cases, there will be no molding window and an warning message indicating there is none. The cause of the error would be the pressure or clamp force being too high. The pressure to fill must be lowered by reducing the maximum flow length by moving the gate or adding gates.

Table 5: Truck Panel Initial Processing Conditions

Parameter ValueMold TemperatureMelt TemperatureInjection Time

48 Chapter 3

To run a filling analysis

1. Ensure the Door Panel MW1 is active and click (File Save Study as) and name it to Door Panel Fill 1.

2. Double-click and set the analysis sequence to Fill.

3. Click Tools Play macro (optional).

3.1. Navigate to the My AMI 2010 Projects\scripts folder.

3.2. Highlight the script MP Intermediate results defining.vbs.

If you can’t find the script, ask your instructor about it.

3.3. Select Edit to open the script in a text editor.

This script intermediate results at specific times during the filling and packing phases, at 0.2 seconds during filling and 1 second during packing. A portion of the script is shown in Figure 17. The full list of result times was omitted to save space.

3.4. Close the editor when done reviewing the script.

3.5. Click Open to play the script and define the intermediate results.

4. Double click (Process settings wizard).

5. Enter the process settings that you determined from the Molding Window Analysis.

6. Click Advanced options.

6.1. Click Edit in the Injection molding machine frame.

6.2. Click the Clamping Unit tab.

6.3. Ensure the clamp force is set to 1200 tonnes.

6.4. Click OK.

6.5. Click Edit in the Solver parameters frame.

6.6. Click the Intermediate Output tab.

6.7. Ensure the filling phase and packing phase regular results have Write at specified times selected, and the times are set as they were in the vbs script.

6.8. Exit from advanced options.

7. Click OK on the Process Setting Wizard dialog.



Figure 17: Example vbs script for setting the intermediate results


1. Open the Analysis Log and view the filling phase results table.

• This will show when the clamp tonnage limit was reached and how the pressure and flow rate changed because of the clamp tonnage limit.

• See Figure 18 as an example.

• Preferably, the clamp tonnage should not be reached. If it is, the later the better.

2. Display Fill time.

2.1. Animate the result to time closest to the time when the clamp force was reached.

There is a significant amount of the part yet to fill when the clamp force was reached.

3. Plot Pressure.

3.1. Animate the result to time step closest to the time when the clamp force was reached.

The clamp force limit was reached so early, there is not much overpacking.

Set Synergy = CreateObject("synergy.Synergy")Synergy.SetUnits "Metric"Set PropEd = Synergy.PropertyEditor()Set Prop = PropEd.FindProperty(10000, 1) '10000 = midplane,10005 =DDSet DVec = Synergy.CreateDoubleArray()DVec.AddDouble 0.2DVec.AddDouble 0.4..DVec.AddDouble 4.6DVec.AddDouble 4.8DVec.AddDouble 5Prop.FieldValues 180, DVec '180 = Write filling phase regular results at times

Set DVec = Synergy.CreateDoubleArray()DVec.AddDouble 6DVec.AddDouble 7DVec.AddDouble 8..DVec.AddDouble 25Prop.FieldValues 182, DVec '182 = Write Packing phase regular results at times

Set DVec = Synergy.CreateDoubleArray()DVec.AddDouble 2DVec.AddDouble 0Prop.FieldValues 198, DVec '198 = filling phase, write results 2 = specified timesSet DVec = Synergy.CreateDoubleArray()DVec.AddDouble 2DVec.AddDouble 0Prop.FieldValues 199, DVec ' 199 = Packing phase, write results 2 = specified timesPropEd.CommitChanges "Process Conditions"

50 Chapter 3

Figure 18: Analysis log filling phase table

Fill Analysis

Residual Stress Analysisanalysis is beginning .... Filling phase: Status: V = Velocity control P = Pressure control V/P= Velocity/pressure switch-over|-------------------------------------------------------------|| Time | Volume| Pressure | Clamp force|Flow rate|Status || (s) | (%) | (MPa) | (tonne) |(cm^3/s) | ||-------------------------------------------------------------|| 0.20 | 3.38 | 8.40 | 4.04 | 565.16 | V || 0.40 | 8.00 | 12.23 | 13.92 | 577.29 | V || 0.60 | 12.71 | 15.01 | 28.11 | 588.28 | V || 0.80 | 17.46 | 17.44 | 47.78 | 590.90 | V || 1.00 | 22.23 | 19.68 | 72.17 | 592.31 | V || 1.20 | 27.01 | 21.72 | 99.69 | 595.33 | V || 1.40 | 31.79 | 23.69 | 131.95 | 597.53 | V || 1.60 | 36.58 | 25.58 | 167.75 | 599.74 | V || 1.80 | 41.37 | 27.39 | 207.58 | 601.17 | V || 2.00 | 46.14 | 29.46 | 262.30 | 600.19 | V || 2.20 | 50.90 | 31.63 | 325.78 | 601.52 | V || 2.40 | 55.66 | 33.71 | 393.19 | 603.12 | V || 2.60 | 60.43 | 35.76 | 466.92 | 603.78 | V || 2.80 | 65.19 | 37.79 | 546.36 | 604.67 | V || 3.00 | 69.96 | 39.78 | 629.40 | 605.92 | V || 3.20 | 74.69 | 42.28 | 748.42 | 605.68 | V || 3.40 | 79.42 | 44.87 | 877.96 | 607.07 | V || 3.60 | 84.14 | 47.52 | 1020.84 | 607.85 | V | ** WARNING 98932 ** The clamp force required to fill/pack the part is greater than the maximum machine clamp force value in the clamping unit properties of the currently selected injection molding machine. The maximum machine clamp force will be maintained in the analysis.| 3.80 | 88.80 | 50.94 | 1200.00 | 608.69 | V || 3.90 | 90.87 | 45.25 | 1200.00 | 393.37 | V || 4.00 | 92.22 | 42.70 | 1200.00 | 310.89 | V || 4.10 | 93.35 | 41.59 | 1200.00 | 266.00 | V || 4.20 | 94.32 | 40.79 | 1200.00 | 234.56 | V || 4.30 | 95.16 | 40.07 | 1200.00 | 205.20 | V || 4.40 | 95.85 | 36.33 | 1200.00 | 133.50 | V || 4.60 | 96.54 | 32.76 | 1200.00 | 86.95 | V || 4.80 | 97.05 | 32.34 | 1200.00 | 73.25 | V || 5.00 | 97.47 | 32.38 | 1200.00 | 65.13 | V || 5.93 | 98.61 | 29.77 | 1200.00 | 27.60 | V/P |

** WARNING 128272 ** Short shot detected. The clamp force of the injection molding machine is insufficient. ------------------------------------------------------------------------


Results interpretation

It is clear just from the analysis log that the single gate option will not work. The clamp force limit was hit early and a short shot was created. Looking at the fill time and pressure plots you can see that a significant area of the part is at high pressure, causing the spike in clamp force.

Finalizing the gate locations

A single gate will not work because the clamp force is too high. Additional gates must be used. Iterate between the gate location analysis, molding window analysis and fill analysis to find and test gate locations. Ensure the gate locations you pick are possible when using a hot runner system on the underside of the part.

To determine the final gate locations

1. Click (File Save All Studies).

2. Activate the Door Panel Fill 1 study and click (File Save Study as) and name it Door Panel Gate Loc 2.

3. Run a gate location analysis.

3.1. Set the analysis sequence to Gate Location.

3.2. Use the number of gate of your choosing.

The fewer gates the better.

3.3. Review the gate location results.

Ensure the gate locations determined by the gate location analysis are possible with a hot runner.

3.4. Move the gates if necessary to make it possible to use the locations.

4. Run a Molding window analysis with the new gate locations.

• With a shorter flow length, the fill time will probably be shorter than with one gate.

5. Run a fill analysis.

5.1. Use the new gate locations and molding conditions determined.

5.2. Ensure the same intermediate results files are selected.

6. Review the results.

6.1. Compare the new results with the first filling analysis.

6.2. Lock the results and tile the windows to look at the results together.

6.3. Look carefully at the pressure plot. This will indicate how well balanced the filling is. Large areas of high pressure contribute to a spike in clamp force.

6.4. Decide if the results are reasonable or they still need adjusting.

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7. Consider one or more of the following changes as needed to get acceptable results.

• Move gate(s) closer to areas that did not fill, or filled later.

• Increase the melt temperature.

• Decrease the injection time.

• Add a gate.

• Use the recommended ram speed profile.

/ Don’t stop at one analysis even if you think the results are good. Try to make them better. For instance, a slight variation in gate location can make a large difference in the filling pattern and clamp force requirements. The plot below shows the position of the flow front with 4 subtle variations in the gate location. In all cases, the camp force is exceeded, but at different times and with different reductions in flow rate. The weld line locations also change. To get this plot, The fill time was set with 20 frames, showing the current frame only, the scale was 0 to 4 sec., making the increment 0.2 sec. and banded color was on.


Design and analyze the feed system

To create a hot runner

1. Click (File Save Study as) on the study with the gate location and processing conditions you like, as a new name such as Door Panel Run 1.

2. Click Modeling Runner System Wizard to create the hot runner.

3. On page one of the wizard, enter:

3.1. Select Center of Mold for placement of the gates.

3.2. Check the I would like to use a hot runner system box.

3.3. Enter 400 mm as the top runner plane.

3.4. Click Next.

4. On page two of the wizard, enter:

4.1. Enter 12 mm as the sprue diameter.

4.2. Enter 0 degrees for the included angle.

4.3. Enter 25 mm as the sprue length.

4.4. Enter the size of your choosing for the runner (manifold).

4.5. Enter the size of your choosing for the drop.

4.6. Click Next.

5. On page three of the wizard, enter:

5.1. Enter the diameters and length of your choosing for the Gates.

5.2. Click Finish to complete the runner system.

The hot manifold created by the wizard may not be practical. Consider replacing it. In Figure 19A, the manifold design is not practical. The manifold has extra 90º bends in it going from the sprue to the drops. A manifold like this would not be built. The manifold would be built more like Figure 19B. The manifold goes straight between the drops.

Figure 19: Manifold curves

The task below steps through the process of fixing the manifold for the gate locations above. Use these steps to fix your manifold system as needed.

/ Make the manifold diameter larger than the drops.

A B

Sprue

Drops

12

3

4

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To revise the runner layout

1. Rename element properties:

1.1. Highlight one of the elements in the manifold.

1.2. Right-click and select Properties.

1.3. Change the property name to Manifold XX mm, where XX is the diameter of it.

Ensure the box Apply to all entities that share this property is checked.

The new name will easily identify this property in the property lists.

2. Delete the elements.

2.1. Click Edit Select by Properties or CTRL + B.

2.2. Select Beam element and Curve as the entity types.

2.3. Select the Manifold you renamed property.

2.4. Click OK.

2.5. Press the Delete key to delete the elements and curves.

2.6. Click OK to accept the entity selection.

2.7. Click Purge Node in the Nodal mesh tools , in the toolbox.

2.8. Click Apply.

3. Create a curve for the manifold between drops 2 and 3.

3.1. Click Create line in the Create curves tools in the toolbox.

3.2. Set the filter to Node.

3.3. Select the node at the end of drop 2 as shown in Figure 19B for the First field.

3.4. Select the node at the end of drop 3 for the Second field.

3.5. Click Apply.

4. Click Nodes by Dividing Curve in the Create Nodes tools in the toolbox.

4.1. Select the curve between drop 2 and 3 just created.

4.2. Enter 3 in the Number of nodes field.

4.3. Click Apply.

5. Create a curve between drop 1 and the curve between drops 2 and 3.

5.1. Click Create line in the Create curves tools in the toolbox.


5.3. Select the node at the center of the curve going between drops 2 and 3, for the Second field.

5.4. Click Apply.


6. Make a LCS to help construct the runners.

6.1. Activate the Runner System layer.

6.2. Click Modeling Local Coordinate System/modeling plane Define.

6.3. Set the filter to Node.


6.5. Select the node at location 4 as shown in Figure 19B for the Second field.

6.6. Select the node at the base of the sprue for the Third field.

6.7. Click Apply.

6.8. Click Close.

6.9. Select the new LCS.

6.10.Right-click select Activate as LCS.

6.11.Click Create line in the Create curves tools in the toolbox.

6.12.Select the node at the base of the sprue for the First field.

6.13.Click the Relative radio button.

6.14.Inter 0 -200 in the Second field.

6.15.Click Apply.

7. Break and delete the curves.

7.1. Click Break Curve in the Create curves tools in the toolbox.

7.2. Click on the 2 curves shown as break 1 in Figure 20.

7.3. Click Apply.

7.4. Click on the 2 curves shown as break 2 in Figure 20.

7.5. Click Apply.

7.6. Click Close.

7.7. Select and delete the node, curve and LCS not needed.

8. Apply the Manifold property to the new curves.

9. Mesh the new curves at the same density as the drops.

• Make sure the Runner layer is active and place the new mesh on the active layer.

Figure 20: Manifold curve construction

Break 1 Break 2

Delete

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To check the balance

1. Run the fill analysis with the same conditions as the study without the runners.

2. View the Fill time plot.

• Make sure the balance is acceptable.

3. View the Weld lines and Air traps.

• Are they still in acceptable locations?

4. View the Analysis Log and check for the clamp force limit.

• When is the limit reached?

• Does the velocity profile change much?

5. View the Pressure.

• Is the pressure distribution acceptable?

If the results are not as balanced as they are in the study without the manifold, the sizes and layout of the hot runner system needs to be adjusted. Either part of the manifold or drops can be changed to fix the problem.

Different philosophies exist on what to change, and you will need to make this decision. Some prefer to change the manifold, others the drops when there is a choice.

To re-run the analysis

1. Make changes as necessary to improve the balance or to fix some other problem.

2. Click (File Save Study as) with a new name.

3. Re-run the analysis.

4. Look at the revised results.

5. Repeat as necessary to get a good result.


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Competency check - Multiple Gates

1. What are the types of multiple gates scenarios that you may have in the part geometry?

2. How do you identify a symmetrical multiple gate scenario?

3. How to identify a non-symmetrical multiple gate scenario?

4. What are the types of analyses recommended by Moldflow to use to aid in the multiple gates optimization process?


60 Chapter 3

Evaluation Sheet - Multiple Gates

1. What are the types of multiple gates scenarios that you may have in the part geometry?

• It can be either symmetrical or non-symmetrical part geometries.

2. How do you identify a symmetrical multiple gate scenario?

• The part will have symmetrical gate locations. And the flow length and pressure drop from each gate will be about the same.

3. How to identify a non-symmetrical multiple gate scenario?

• The part will not have symmetrical gate locations. And the flow length and pressure drop from each gate will not be the same, therefore it is more difficult to optimize.

4. What are the types of analyses recommended by Moldflow to use to aid in the multiple gates optimization process?

• The user should run a set of molding window analysis and fast filling analysis to aid in the number and location of the gates on the part. Then the runner system should be added balanced and further filling and packing analyses should be run to finalize the filling of the part.


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CHAPTER 4

Packing Optimization

Aim

The aim of this chapter is to learn how to produce a uniform volumetric shrinkage through a part with the use of a packing profile. The volumetric shrinkage distribution should be as small as possible.

Why do it

When there is a uniform volumetric shrinkage across the part, the likelihood of warpage is reduced. Warpage is simply caused by a variation in shrinkage, therefore, when the shrinkage variation is reduced, so is the warpage.

Overview

To create a packing profile, the filling and cooling of the part filling should be optimized first. Packing is influenced by the way a part is cooled; therefore, it is best to produce the packing profile based on cooling results. An initial constant packing profile is run. From this information, an initial packing profile is produced, and then modified as necessary to produce the desired results. This technique will be demonstrated on Dual Domain and 3D models, and can be used with a midplane mesh as well.

Packing Optimization 63

64 Chapter 4

Practice - Packing Optimization

This chapter has two models that are used for practice and are described below. One is a Dual Domain model the other is 3D. Do the practice for the model of the mesh type you use most. Do the other as time permits.

Table 6: Models used for packing optimization

Description ModelSnap Cover: starts on page 67

This part uses a Dual Domain mesh. Use this part if your primary mesh type you use is Dual Domain or midplane.

Snap Cover3: starts on page 85

This part uses a 3D tetrahedral mesh. Use this part if your primary mesh type you use is 3D.

Practice - Packing Optimization 65

66 Chapter 4

Snap cover with a Dual Domain mesh

Design criteriaThe packing profile for the snap cover must be optimized. The cooling analysis has already been done. The initial processing conditions and criterion are shown in Table 7. Determine a packing profile to minimize the volumetric shrinkage. Review the results on the initial packing analysis and make modifications to the profile will reduce the volumetric shrinkage.

Project setup

To open a project

1. Click (File Open Project), and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Packing_optimization and double click the project file packing_optimization.mpi.

2. Click File Preferences

2.1. On the General tab, ensure that Active Units are set to Metric.

2.2. On the Directories tab, ensure Default to project directory is checked.

To review the model

1. Open the study SC Fill.

• This study will be used to determine the initial packing pressure.


3. Turn on and off the layers.

• Notice there is several layers for the part itself. These can be used to aid in the interpretation of the results.

Table 7: Snap cover parameters

Parameter ValueModel Type Dual DomainMaterial Maplen EP301K (PP)Mold Temperature 25º CMelt Temperature 220º CInjection + Cooling + Packing 15 secondsInjection Time 1.0 secondInitial Packing Pressure 100 % fill pressureInitial Packing Time 9 secondsTarget Maximum Shrinkage Variation

2% on the body of the part


To run a fill analysis

1. Double-click (Select Materials) and pick the material Basell Australia, Moplen EP301K.

2. Double-click (Process Settings) and enter the parameters shown in Table 8.


Optimizing a packing profileDeveloping an optimized packing profile for a part requires the following basic steps:

1. Determine an initial packing pressure.

2. Determine an initial packing time.

3. Run the first packing analysis, with a constant pressure.

4. Review the packing results for:

Volumetric shrinkage.

Pressure.

Frozen layer fraction.

5. Create an initial packing profile based on the results from the first packing analysis.

6. Run the packing analysis with the packing profile.



Pressure.

Frozen layer fraction.

8. Revise the packing profile and re-run the results as necessary to reduce the volumetric shrinkage variation.

Follow the tasks below to optimize the volumetric shrinkage.


Parameter ValueMold Temperature 25º CMelt Temperature 220º CFilling control Time, 1 secondVelocity/pressure switch-over AutomaticPack/holding control %Filling pressure vs timePacking profile 0

10100100

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Determining an initial packing pressureWhen clamp force is an issue or may be one, it is important to calculate the maximum packing pressure that could be used. The calculation assumes a uniform pressure distribution across the part. This is a conservative estimate as there will never be a uniform pressure distribution. The maximum packing pressure can be estimated by the formula below:

where:

If this calculation indicates the maximum pressure to be at or below the fill pressure, the clamp force may be a significant problem and will limit the packing pressure to the value calculated. If however the calculated pressure is well above the pressure required to fill the part, the packing pressure can be any value required to get the volumetric shrinkage distribution required. A good starting point is a packing pressure that is 80% to 100% of the filling pressure.

To calculate the maximum packing pressure

1. Review the model details section in the Analysis Log from the SC Fill study and find the total projected area of the part.

1.1. Record the value in Table 9.

• Figure 21 shows an example of the Analysis Log.

2. Find the maximum injection pressure.

• This will be listed in the Analysis Log, or the result pressure at V/P switch-over result. This will be the reference pressure for the packing.


3. Calculate the maximum packing pressure given the molding machine clamp force listed in Table 9, using above.

• The maximum packing pressure by the calculation is well above the V/P switchover pressure. Therefore, the packing pressure that can be used for part is not limited by clamp force. The packing pressure in the analysis is 100% of the fill pressure and is a good starting point.

4. Record the packing pressure as 100% in Table 9.

PmaxMachine Clamp force limit

Total projected area of the shot-------------------------------------------------------------------------- Unit conversion 0.8××=

Pmax The maximum packing pressure that can be used.=

Machine clamp force limit Tonnes(metric) or tons(US / English units)=Total projected area of the shot cm^2 or inches^2=

Unit conversion 100 for metric units, 2000 for english units=0.8 Safety factor to only use 80% of machine capacity=

/ The packing pressure can be expressed as a percentage, or pressure. If a pressure is used, it can be rounded to the nearest 1 MPa.


Figure 21: Example fill analysis Analysis Log

Determine an initial packing timeThe packing is optimized on a part that already has cooling run on it. The initial packing time is based on the Injection+Packing+Cooling (IPC) time defined in the cooling analysis. Subtract the injection time from the IPC time. This time should be more than enough to ensure that the gate has frozen with pressure still being applied.

To determine the initial packing time

1. Open the model SC Flat Prof.

2. Double-click (Process Settings) and find the IPC time and record it in Table 10.

3. Determine the fill time for the analysis SC Fill and record it in Table 10.

Model details : Mesh Type = Dual Domain Mesh match percentage = 89.6 %

Reciprocal mesh match percentage = 88.1 % Total number of nodes = 2604 Total number of injection location nodes = 1 The injection location node labels are: 4979 Total number of elements = 5172 Number of part elements = 5118 Number of sprue/runner/gate elements = 51 Number of channel elements = 0 Number of connector elements = 3 Parting plane normal (dx) = 0.0000 (dy) = 0.0000 (dz) = 1.0000 Average aspect ratio of triangle elements = 1.8812 Maximum aspect ratio of triangle elements = 5.5040 Element number with maximum aspect ratio = 5241 Minimum aspect ratio of triangle elements = 1.1547 Element number with minimum aspect ratio = 2459 Total volume = 17.3737 cm^3 Volume filled initially = 0.0000 cm^3 Volume to be filled = 17.3737 cm^3 Part volume to be filled = 10.0589 cm^3 Sprue/runner/gate volume to be filled = 7.3148 cm^3 Total projected area = 49.1242 cm^2

Table 9: Packing pressure calculation data

Parameter ValueMolding machine clamp force limit 75 tonnesPart projected areaPressure at V/P switchoverMaximum packing pressure (Calculated)Packing pressure (used) %

70 Chapter 4

4. Subtract the fill time from the IPC time and round down to the nearest second.

5. Record the value in Table 10.

Run the first packing analysisThe first packing analysis is done with a constant packing pressure for a time long enough for the gate to freeze off.

To run the first flow analysis

1. Activate the SC Flat Prof. study.

2. Double-click (Analysis Sequence) and set the sequence to Cool + Fill + Pack.



Table 10: Determine the packing time

Parameter ValueIPC timeFill timeInitial packing time (calculated)


Parameter ValueMold Temperature 25º CMelt Temperature 220º CMold-open time 5 secondsInjection + packing + Cooling time 15 secondsFilling control Injection timeFill time 1 secondVelocity/pressure switch-over AutomaticPack/holding control %Filling pressure vs timePacking profile 0

Pack time from Table 10Pack pressure from Table 9Pack pressure from Table 9

3 The study has intermediate results defined by specified times. The times were primarily set up too have finer increments around the time the gate is freezing.


Review the packing results

Volumetric shrinkage as a shaded image

To view the Volumetric Shrinkage at ejection results

1. Ensure that only the following layers are turned on:

• Body.

• Detail.

• Gate.

• Runners.

2. Click on Volumetric shrinkage at ejection result.

3. Click off the layers in the following order.

Runners.

Gate.

Detail.

• Watch the scale change as layers are turned off.

• Rotate the part so you can see the detail as it is turned off.

4. Ensure that only the Body layer is turned on.

Volumetric shrinkage interpretation

Results are automatically scaled by visible layers which makes it easy to scale results to portions of the model of interest. The volumetric shrinkage will NOT be uniform if you consider small detail that is thick or thin. The volumetric shrinkage distribution used for optimization should concentrate on the main body of the part. The shrinkage is rather low at the gate, and rather high end of fill. The shrinkage distribution indicates that the gate area is over packed. Preferably, the volumetric shrinkage variation across the part should be under 2%.

Volumetric shrinkage as a path plot

A volumetric shrinkage path plot is an excellent way to watch how volumetric shrinkage changes over time.

To create volumetric shrinkage path plot results

1. Click (Results New Plot).

2. Select Volumetric shrinkage from the Available results list.

3. Click Path plot as the plot type, then OK.

4. Click on 25 to 30 points on the part from the gate location to the end of the fill as

shown in Figure 22. Click to add the points if not already active.

5. Click (Select) when done to stop picking points to add.

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Figure 22: Path plot locations for volumetric shrinkage

6. Click (Results Plot Properties) and set the Y-axis scale from 0 to 10.5.

7. Click (Animate results).

Volumetric shrinkage path plot interpretation

Initially, the volumetric shrinkage is high, about 10% but quickly the volumetric shrinkage drops. As the shrinkage drops, the shrinkage is fairly uniform across the part until the part begins to freeze. Then areas closer to the gate begin to drop considerably lower than the areas at the end of fill.

Pressure results

To create an XY plot of pressure


2. Select Pressure in the Available plot list.

3. Select XY Plot in the Plot type list.

4. Click OK to create the plot.

5. Enter in the Entity IDs dialog that opens, the following nodes, then press Enter:

• 4979, 2482, 3002, 2709, 2805.

6. Click (Select) to stop picking entities.

Pressure XY interpretation

Node 4979 is at the top of the sprue and node 2805 is at the end of fill. The others go from near the gate to the end of fill. There is about a 10 MPa pressure difference between the gate and end of fill when the end of fill is at its peak pressure. The gate area also has a higher pressure for a much longer time. This results in the over packing as shown in the volumetric shrinkage results.

The traces of the nodes plotted should be nearly on top of one another during packing to have a uniform volumetric shrinkage. You will create a decayed packing profile to achieve a more uniform volumetric shrinkage.


To create the first decayed packing profile, determine the constant pressure time and the decay time. The transition point is between the constant pressure time and the decay time, as shown in Figure 23, and is based on the pressure trace of node at the end of fill (2805). The transition point is defined by a point midway between the time when the pressure is maximum and the time which the pressure reaches zero. The decay will then be linear going to zero when the gate freezes.

Figure 23: Packing profile components

To determine the constant pressure time

1. Click (Examine results).

2. Click the data point at the time for node 2805 when:

2.1. The pressure is at its maximum.

2.2. The pressure goes to zero.

2.3. Record the values in Table 12 on page 75.

3. Find average time between these two times.

3.1. Round the average to 0.1 seconds.


• This average defines the transition point.

4. Open the Analysis Log and locate the V/P switchover time in the filling phase status table.

4.1. Round it to 0.1 seconds.


5. Subtract the V/P switchover time from the transition point.


• This defines the constant pressure time.

Determine the Decay time

The frozen layer fraction is used to calculating the decay time by determining the time when the gate is frozen and subtracting the transition point time.

Time

Pres

sure

Constant pressure time

Decay time

Transition point

Pressure at zero

74 Chapter 4

To plot the frozen layer fraction

1. Ensure only the Gate and Body layers are on.

2. Click the Frozen Layer Fraction plot.

3. Click (Results Plot Properties), and uncheck Nodal averaged from the Optional Setting tab.

4. Rotate and zoom up on the gate area so you can see the gate and surrounding area of the part.

5. Click (Step Backward) to animate the result one frame at a time.

5.1. Start at its maximum time and step backwards one step at a time until the gate is just frozen.

The gate and part should have a frozen layer fraction of 1.0, which represents gate freeze.

In some cases when the gate is thicker, most if not all the part may have a frozen layer fraction of 1.0 before the gate. Use your best judgement to determine at what time the part can no longer be effectively packed. A long estimate is conservative.


6. Subtract the transition point from the gate freeze time.

6.1. Record the value in Table 12 as the decay time.

To determine the pack pressure

1. Open the Analysis Log and locate the Pressure at the end of fill, in the filling phase status table.

1.1. Round it to nearest 1 MPa.


• The first packing analysis set the packing pressure as a percentage of the fill pressure, in this case 100%. For all subsequent packing analyses, the packing pressure is set by packing pressure directly. Examine the Analysis Log file to determine what that pressure is.

Table 12: Values for calculating the first injection profile

Description ValueTime when end of fill node reaches maximum pressureTime when end of fill node at 0 pressureAverage between the first two times (Transition point)V/P switchover timeTransition point - V/P switchover time (Constant pressure time)Gate freeze time


Create an initial packing profileReviewing the results from the packing analysis with a constant profile is used to write the first packing profile. The packing profile is described in Table 13.

Run the second packing analysisThe second packing analysis is done with the decayed packing profile defined above.


1. Activate the SC Flat Prof. study.

2. Click (File Save study as) and enter the name SC Prof 1.


3.1. Click the Plot Profile button on the Pack/Holding Control Profile Settings dialog to see the shape of the profile. It should look similar to Figure 24.


Gate freeze time - Transition point (Decay time)Packing Pressure

Table 13: First decayed packing profile

Time Duration[Sec]

Pressure[MPa]

Description

0.2 The time duration is 0.2 seconds. This is the time required to go from the V/P switchover to the packing pressure. This time is used to allow the machine to react to the pressure change. The pressure is the Packing pressure defined in Table 12.The time duration is the Constant pressure time - 0.2 seconds defined from Table 12. The pressure is the same packing pressure used above.

0 The time duration is the decay time defined in Table 12.


Description Value

Table 14: SC Prof 1 parameters

Parameter ValueMold Temperature 60º CMelt Temperature 240º CMold-open time 5 secondsInjection + packing + Cooling time 21 secondsFilling control Injection timeFill time 1 second

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Figure 24: Shape for the SC Prof 1 packing profile


Volumetric shrinkage results

To review the volumetric shrinkage results

1. Ensure that only SC Flat Prof and SC Prof 1 studies are the only open studies.


3. Click View Lock and choose all of the locks, one at a time.

4. Ensure only the Body layer is on for both studies.

5. Click in the SC Flat Prof study to select it.

6. Click Volumetric shrinkage at ejection to display the result.

• The result should be displayed in both studies.

• Note the differences in the ranges.

6.1. Click (Plot Properties) and set the scale to the range that encompasses both parts.

7. Rotate the parts to see the variation in shrinkage.

Velocity/pressure switch-over AutomaticPack/holding control Packing pressure vs timePacking profile As written in Table 13


Parameter Value


To plot volumetric shrinkage with a path plot

1. Click in the SC Flat Prof study to select it.

2. Click Volumetric shrinkage:Path Plot to activate it.

• The plot will automatically be created in the SC Prof 1 study because the plots are locked between the studies.

3. Click (Step Forward) to animate the result one frame at a time for the SC Prof 1 study.

3.1. Look for the last time step where the curve’s slope is about constant. On the next time step, the slope’s right side slows its reduction in shrinkage and the left side (starting at about 25 mm) decays faster.

This will be a subtle change and should be around 6 seconds.

3.2. Record the time in Table 15. This is the knee point.


You should see that the over packing on the gate half of the part has been reduced but not enough. The shrinkage is still quite a bit lower on the gate half of the part as compared to the end of fill except for the spike in shrinkage at the gate. The path plot confirms that the shrinkage at the end of fill is similar. The next profile should address the spike in shrinkage right at the gate and the general trend of lower shrinkage on the gate end of the part compared to the end of fill.

Determine the gate freeze time

To plot frozen layer fraction

1. Click in the SC Prof 1 study to activate it.

2. Click the Gate layer to activate it.

3. Click in the SC Flat Prof study to activate it.

4. Click the Frozen layer fraction plot to activate it.

5. Click (Step Backward) to animate the result one frame at a time to determine when the gate freezes for SC Prof 1.

6. Record the value in Table 15 rounded to 0.1 seconds.

Gate freeze interpretation

Due to the decay in the profile, the gate freezes faster than the first analysis with a constant pressure profile.

78 Chapter 4

Pressure results

To plot pressure:XY

1. Click in the SC Flat Prof study to activate it.

2. Click the Pressure:XY plot to activate it.

• This will create the result in the SC Prof 1 study.


Pressure results interpretation

Nodes 2482 and 3002 which represent areas closer to the gate have significantly been influenced by the profile. However, to make the volumetric shrinkage have a smaller range across the part, the pressure traces need to become closer. The decay needs to be faster. The pressure decay needs to be changed based on the node 2805 and the volumetric shrinkage path plot.

To revise the packing profile


2. Query the curve for node 2805 to find the pressure at the knee point.

• This time was found in a previous task and recorded in Table 15.

2.1. Record the pressure in Table 15 to 1 MPa.

• This will represent the knee point pressure for the new profile.

3. Record in Table 15 the transition point that was calculated in Table 12.

4. Calculate the profile’s decay to the knee point by subtracting the transition point from the knee point.

4.1. Record the value in Table 15 to 0.1 seconds.

5. Calculate the decay to zero by subtracting the knee point from the gate freeze time.

5.1. Record the value in Table 15 to 0.1 seconds.

6. Write the new packing profile in Table 16 based on the information calculated in Table 15.

Table 15: Values for calculating the second injection profile

Description Value Knee pointGate freeze timeTransition point from Table 12Knee point pressureTime to knee pointDecay time to zero


Run the third packing analysisThe second packing analysis is done with the decayed packing profile defined above.


1. Activate the SC Prof 1 study.

2. Click File Save study as and enter the name SC Prof 2.


3.1. Click the Plot Profile button on the Pack/Holding Control Profile Settings dialog to see the shape of the profile. It should look like Figure 25.

4. Double-click (Continue analysis).

.

Table 16: Second decayed packing profile

Time Duration[Sec]

Pressure[MPa]

Description

0.2 Use the same duration and pressure as Table 13.Use the same constant pressure time and pressure as Table 13.The time duration is the Decay to the knee calculated in Table 15.

0 The time duration is the decay time to zero as calculated in Table 15.


Parameter ValueMold Temperature 50º CMelt Temperature 230º CMold-open time 5 secondsInjection + packing + Cooling time 21 secondsFilling control Injection timeFill time 1 secondVelocity/pressure switch-over AutomaticPack/holding control Packing pressure vs timePacking profile As written in Table 16

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1. Ensure that only SC Prof 1 and SC Prof 2 studies are the only open studies.


3. Click View Lock and choose all of the locks on at a time.

4. Ensure only the Body layer is on for both studies.

5. Click in the SC Prof 1 study to select it.

6. Click Volumetric shrinkage at ejection to display the result.

• The result should be displayed in both studies.

6.1. Click (Plot Properties).

6.2. Set the Scaling to All frames.

6.3. Click Apply to see the full scale for each part.

6.4. Set the scale to the range that encompasses both parts.

7. Rotate the parts to see the variation in shrinkage.

To plot volumetric shrinkage as a path plot

1. Click in the SC Prof 1 study to select it.

2. Click Volumetric shrinkage:Path Plot to activate it.

• The plot will automatically be created in the SC Prof 2 study because the plots are locked between the studies.

3. Select (Plot Properties).


4. Click (Step Forward) to animate the result one frame at a time for the SC Prof 2 study.

4.1. Look for the first time step where the curve’s slope does not change any more except for the first portion close to the gate.

This will be a subtle change and should be around 6 seconds.

4.2. Record the time in Table 18. This is the second knee point.


The volumetric shrinkage with SC Prof 2 is now much more uniform across most of the part. However, the shrinkage is now too high near the gate in SC Prof 2. The profile goes to zero too quickly. The next analysis will keep the pressure high once most of the part has frozen to pack the area around the gate better.

Pressure results

To plot pressure:XY

1. Click in the SC Prof 1 study to activate it.


• This will create the result in the SC Prof 2 study.



5. Query the curve for node 4979 to find the pressure at the second knee point.

• This time was found in a previous task and recorded in Table 18.

5.1. Record the pressure in Table 18 to 1 MPa.

• This will represent the second knee point pressure for the new profile.

• The first 3 steps of the new profile will be the same as the last profile.

• This new profile will maintain the pressure at the knee for one second then decay to zero in one second

6. Write the new packing profile in Table 19 based on the information calculated in Table 18.

Table 18: Values for calculating the third injection profile

Description Value Second knee pointPressure at second knee pointTime to knee point (first knee, in Table 15)Second knee point minus first knee point

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Run the fourth packing analysisThe third packing analysis is done with the decayed packing profile defined above.


1. Activate the SC Prof 2 study.

2. Click File Save study as and enter the name SC Prof 3.


3.1. Click the Plot Profile button on the Pack/Holding Control Profile Settings dialog to see the shape of the profile. It should look like Figure 26.

4. Double-click (Continue analysis)

Table 19: Third decayed packing profile

Time Duration[Sec]

Pressure[MPa]

Description

0.2 Use the same duration and pressure as Table 16.Use the same constant pressure time and pressure as Table 16.The time same time to the knee as in Table 16.Difference between the first and second.knee points, and pressure at second knee point.

1 Maintain second knee point pressure for one second.1 0 One second to decay to zero pressure.


Parameter ValueMold Temperature 50º CMelt Temperature 230º CMold-open time 5 secondsInjection + packing + Cooling time 21 secondsFilling control Injection timeFill time 1 secondVelocity/pressure switch-over AutomaticPack/holding control Packing pressure vs timePacking profile As written in Table 19



Review resultsUse the same techniques as before to review the results of the last analysis and compare it to previous analyses.

SummaryEvery part and material is different. The shape of the profile will change in each situation. The size of the gate can make a significant difference. In this case, the gate is about half the nominal wall and did not freeze until most of the part. As a result, the profile needed to account for a long freeze time. If the gate were smaller, the gate may freeze too early, making it more difficult to get the shrinkage distribution desired.

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Snap cover with a 3D mesh

Design criteriaThe packing profile for the snap cover must be optimized. The cooling analysis has already been done. The initial processing conditions and criterion are shown in Table 21. Determine a packing profile to minimize the volumetric shrinkage. Review the results on the initial packing analysis and make modifications to the profile will reduce the volumetric shrinkage.

Project setup

To open a project

1. Click (File Open Project) and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Packing_optimization and double click the project file packing_optimization.mpi.

2. Click File Preferences

2.1. On the General tab, ensure that Active Units are set to Metric.

2.2. On the Directories tab, ensure Default to project directory is checked.

To review the model

1. Open the study SC3 Fill.

• This study will be used to determine the initial packing pressure.




Parameter ValueModel Type 3DMaterial SunAllomer PM870A (PP)Mold Temperature 35º CMelt Temperature 230º CInjection + Cooling + Packing 12 secondsInjection Time 1.0 secondInitial Packing Pressure 80 % fill pressureInitial Packing Time 10 secondsTarget Maximum Shrinkage Variation

2% on the body of the part


To run a fill analysis

1. Double-click (Select materials) and pick the material SunAllomer Ltd, SunAllomer PM870A.



Optimizing a packing profileDeveloping an optimized packing profile for a part requires the following basic steps:

1. Determine an initial packing pressure.

2. Determine an initial packing time.

3. Run the first packing analysis, with a constant pressure.



Pressure.

Temperature.

5. Create an initial packing profile based on the results from the first packing analysis.

6. Run the packing analysis with the packing profile.



Pressure.

Temperature.

8. Revise the packing profile and re-run the results as necessary to reduce the volumetric shrinkage variation.

Follow the tasks below to optimize the volumetric shrinkage.


Parameter ValueMold Temperature 35º CMelt Temperature 230º CFilling control Time, 1 secondVelocity/pressure switch-over By %volume filled, 99%Pack/holding control %Filling pressure vs timePacking profile 0

10100100

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Determining an initial packing pressureWhen clamp force is an issue or may be one, it is important to calculate the maximum packing pressure that could be used. The calculation assumes a uniform pressure distribution across the part. This is a conservative estimate as there will never be a uniform pressure distribution. The maximum packing pressure can be estimated by the formula below:

where:

If this calculation indicates the maximum pressure to be at or below the fill pressure, the clamp force may be a significant problem and will limit the packing pressure to the value calculated. If however the calculated pressure is well above the pressure required to fill the part, the packing pressure can be any value required to get the volumetric shrinkage distribution required. A good starting point is a packing pressure that is 80% to 100% of the filling pressure.

To calculate the maximum packing pressure

1. Review the model details section in the Analysis Log from the SC3 Fill study and find the total projected area of the part.

1.1. Record the value in Table 23 on page 88.

• Figure 21 shows an example of the Analysis Log.

2. Find the maximum injection pressure.

• This will be listed in the Analysis Log, or the result pressure at V/P switch-over result. This will be the reference pressure for the packing.


3. Calculate the maximum packing pressure given the molding machine clamp force listed in Table 23, using above.

• The maximum packing pressure by the calculation is well above the V/P switchover pressure. Therefore, the packing pressure that can be used for part is not limited by clamp force. The packing pressure in the analysis is 100% of the fill pressure and is a good starting point.

4. Choose the packing pressure you would like to use and record it in Table 9.

PmaxMachine Clamp force limit

Total projected area of the shot-------------------------------------------------------------------------- Unit conversion 0.8××=

Pmax The maximum packing pressure that can be used.=

Machine clamp force limit Tonnes(metric) or tons(US / English units)=Total projected area of the shot cm^2 or inches^2=

Unit conversion 100 for metric units, 2000 for english units=0.8 Safety factor to only use 80% of machine capacity=

/ The packing pressure can be expressed as a percentage, or pressure. If a pressure is used, it can be rounded to the nearest 1 MPa.


Figure 27: Example fill analysis Analysis Log

Determine an initial packing timeThe packing is optimized on a part that already has cooling run on it. The initial packing time is based on the Injection+Packing+Cooling (IPC) time defined in the cooling analysis. Subtract the injection time from the IPC time. This time should be more than enough to ensure that the gate has frozen with pressure still being applied.

To determine the initial packing time

1. Open the model SC3 Flat Prof.

2. Double-click (Process Settings) and find the IPC time and record it in Table 24.

Model Details:============= Mesh Type = 3D Tetrahedra Laminates across radius of beam elements = 12 Total number of nodes = 8517 Number of 3D nodes = 8496 Number of HS nodes = 20 Number of interface nodes = 1 Total number of injection location nodes = 1 The injection location node numbers are: 8583

Total number of elements = 44132 Number of part elements = 44132 Number of tetrahedral elements = 44112 Number of sprue/runner/gate elements = 20

Total volume = 14.0016 cm^3 Volume of tetrahedral elements = 8.9953 cm^3 Volume of sprue/runner/gate elements = 5.0063 cm^3 Volume filled initially = 0.0000 cm^3 Volume to be filled = 14.0016 cm^3 Part volume to be filled = 8.9953 cm^3 Sprue/runner/gate volume to be filled = 5.0063 cm^3 Parting plane normal (dx) = 0.0000 (dy) = 0.0000 (dz) = 1.0000 Total projected area = 46.5483 cm^2--------------------------------------------------------------------

Table 23: Packing pressure calculation data

Parameter ValueMolding machine clamp force limit 75 tonnesPart projected areaPressure at V/P switchoverMaximum packing pressure (Calculated)Packing pressure (used) %

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3. Determine the fill time for the analysis SC3 Fill and record it in Table 24.

4. Subtract the fill time from the IPC time and round down to the nearest second.

5. Record the value in Table 24.

Run the first packing analysisThe first packing analysis is done with a constant packing pressure for a time long enough for the gate to freeze off.


1. Activate the SC3 Flat Prof. study.

2. Double-click (Analysis sequence) and set the sequence to Cool + Fill + Pack.


4. Double-click Start Analysis.

Table 24: Determine the packing time

Parameter ValueIPC timeFill timeInitial packing time (calculated)


Parameter ValueMold Temperature 35º CMelt Temperature 230º CMold-open time 5 secondsInjection + packing + Cooling time 12 secondsFilling control Injection timeFill time 1 secondVelocity/pressure switch-over By %volume filled, 99%Pack/holding control %Filling pressure vs timePacking profile 0

Pack T from Table 24Pack pressure from Table 23Pack pressure from Table 23

3 The study has intermediate results defined by specified times. The times were primarily set up too have finer increments around the time the gate is freezing.



Volumetric shrinkage by a single contour

To view the Volumetric Shrinkage results

1. Ensure that only the Part layer is turned on.

2. Click the Volumetric shrinkage result.

3. Click (Results Plot Properties) to set up the results.

3.1. Click the Animation tab.

Set Single dataset for the Animate result over.

Set the time to the last one in the Animate result at list.

Click the Apply button to update the model based on the settings so far.

Record the range of volumetric shrinkage to the nearest 0.25% on the part, shown on the scale on the right side of the screen, in Table 26.

3.2. Click the Scaling tab.

Click the Specified button.

Set the Min and Max to the values listed in Table 26.

3.3. Click on the Animation tab.


Click the Value Range button.

Enter a value of 0.25.

Click the Current frame only button.

Click OK

4. Click (Step Forward) to animate the result one frame at a time.

• Watch how the shrinkage ranges appear and disappear on the part as the range plotted gets higher.


The lowest shrinkage is in and near the gate and end of fill. As the shrinkage range gets higher, the shrinkage contour covers the entire part. As the range continues to get higher, there is no longer any contour in the gate end of the part, indicating the gate area has shrinkage values only lower then the range plotted. As the plotted range gets higher, the area at the plotted shrinkage value gets smaller, with the highest shrinkage at the end of fill.

Table 26: Volumetric shrinkage range

Volumetric shrinkage Min MaxSC3 Flat Prof

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The goal of packing optimization is to make the volumetric shrinkage more uniform. The portion of the cross-section with the higher shrinkage should be throughout the part, not just at one end.

Volumetric shrinkage as a Probe XY plot

A volumetric shrinkage probe XY plot is an excellent way to watch how volumetric shrinkage changes through the thickness and over time.

To create volumetric shrinkage probe XY plot results

1. Click (Front view) to rotate the part to 0, 0, 0.


3. Select Volumetric shrinkage from the Available results list.

4. Click Probe XY plot as the plot type, then OK.

5. Click on the 5 locations shown in Figure 28 starting by the gate.

• Click to activate and pick the locations.

6. Click to stop selecting locations on the part to graph.

Figure 28: Path plot locations for volumetric shrinkage

7. Click (Plot Properties) and set the Y-axis scale from 4 to 17 on the XY Plot Properties (2) tab.

8. Click (Animate results).

Volumetric shrinkage probe XY plot interpretation

Initially, the volumetric shrinkage is very high in the center of the cross section, nearly 17%. As the packing time increases, the volumetric shrinkage decreases significantly, particularly in the center of the part. At the end of the cycle, the highest shrinkage in the center of the cross section is at the end of fill. Curve 2 which is not far from the gate, has the lowest shrinkage then gradually increases to the end of fill.

1 2 3 4 5


Pressure results

To create an XY plot of pressure


2. Select Pressure in the Available plot list.

3. Select XY Plot in the Plot type list.

4. Click OK to create the plot.

5. Enter in the Entity IDs dialog that opens the following nodes, then press Enter:

• 40750, 2681, 1136, 1614, 2372.

6. Click (Select) to stop picking entities.

Pressure XY interpretation

Node 40750 is at the top of the sprue and node 2372 is at the end of fill. The others go from near the gate to the end of fill. There is about a 7 MPa pressure difference between the gate and end of fill when the end of fill is at its peak pressure. The gate area also has a high pressure for a much longer time. This results in the over packing as shown in the volumetric shrinkage results.

The traces of the nodes plotted should be nearly on top of one another during packing to have a uniform volumetric shrinkage. You will create a decayed packing profile to achieve a more uniform volumetric shrinkage.

To create the first decayed packing profile, determine the constant pressure time and the decay time. The transition point is between the constant pressure time and the decay time, as shown in Figure 29, and is based on the pressure trace of node at the end of fill (2372). The transition point is defined by a point midway between the time when the pressure is maximum and the time which the pressure reaches zero. The decay will then be linear going to zero when the gate freezes.

Figure 29: Packing profile components

Time

Pres

sure

Constant pressure time

Decay time

Transition point

Pressure at zero

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To determine the constant pressure time


2. Examine the time for the end of fill node (2372) when:

2.1. The pressure is at its maximum.

2.2. The pressure goes to zero.

2.3. Record the values in Table 27 on page 94.

3. Find average time between these two times.

3.1. Round the average to 0.1 seconds.


• This average defines the transition point.

4. Open the Analysis Log and locate the V/P switchover time in the filling phase status table.

4.1. Round it to 0.1 seconds.


5. Subtract the V/P switchover time from the transition point.


• This defines the constant pressure time.

Determine the Decay time

The Temperature result set as a single contour at the transition temperature is used to calculating the decay time by determining the time when the gate is frozen and subtracting the transition point time.

To determine the transition temperature

1. Right-click and select Details.

2. Click on the Rheological Properties tab.

3. Record the Transition temperature. _______ºC

To plot the Temperature result

1. Ensure only the Part layer is on.

2. Click the Temperature plot.



3.1. Click the Methods tab.

3.2. Click the Contour button.

3.3. Check the Single Contour box.

3.4. Enter the transition temperature found above in the Contour value field.

3.5. Click OK.

4. Zoom up on the gate area so you can see the gate and surrounding area of the part.

5. Click (Step Backward) to animate the result one frame at a time to determine when the gate freezes.

• The gate is frozen at the earliest time step with the contour separates, as shown in Figure 30.


6. Subtract the transition point from the gate freeze time.


Figure 30: Gate just frozen

To determine the pack pressure

1. Open the Analysis Log and locate the Pressure at the end of fill, in the filling phase status table.

1.1. Round it to nearest 1 MPa.


• The first packing analysis set the packing pressure as a percentage of the fill pressure, in this case 100%. For all subsequent packing analyses, the packing pressure is set by packing pressure directly. Examine the Analysis Log file to determine what that pressure is.


Description ValueTime when end of fill node reaches maximum pressure

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Create an initial packing profileReviewing the results from the packing analysis with a constant profile is used to write the first packing profile. The packing profile is described in Table 28.

Run the second packing analysisThe second packing analysis is done with the decayed packing profile defined above.


1. Activate the SC3 Flat Prof. study.

2. Click File Save study as and enter the name SC3 Prof 1.

3. Double-click (Injection location) to delete the results copied from SC3 Flat Prof.


4.1. Click the Plot Profile button on the Pack/Holding Control Profile Settings dialog to see the shape of the profile. It should look similar to Figure 31.

Time when end of fill node at 0 pressureAverage between the first two times (Transition point)V/P switchover timeTransition point - V/P switchover time (Constant pressure time)Gate freeze timeGate freeze time - Transition point (Decay time)Packing Pressure

Table 28: First decayed packing profile

Time Duration[Sec]

Pressure[MPa]

Description

0.2 The time duration is 0.2 seconds. This is the time required to go from the V/P switchover to the packing pressure. This time is used to allow the machine to react to the pressure change. The pressure is the Packing pressure defined in Table 27.The time duration is the Constant pressure time - 0.2 seconds defined from Table 27. The pressure is the same packing pressure used above.

0 The time duration is the decay time defined in Table 27.


Description Value


5. Double-click the Start Analysis icon .

Figure 31: Shape for the SC3 Prof 1 packing profile


Volumetric shrinkage results


1. Ensure that the SC3 Prof 1 is active, only the Part layer is turned on and results are not locked.

2. Click on Volumetric shrinkage result.

Table 29: SC3 Prof 1 parameters

Parameter ValueMold Temperature 35º CMelt Temperature 230º CMold-open time 5 secondsInjection + packing + Cooling time 10 secondsFilling control Injection timeFill time 1 secondVelocity/pressure switch-over By %volume filled, 99%Pack/holding control Packing pressure vs timePacking profile As written in Table 28

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3. Click (Results Plot Properties) to set up the results.


Set Single dataset for the Animate result over.

Set the time to the last one in the Animate result at list.

Click the OK button to update the model based on the settings so far.

Record the volumetric shrinkage range to the nearest 0.25% in Table 30.


Click the Specified button.

Set the Min and Max to the values listed in Table 30 on page 97 encompassing both the SC3Flat Prof and SC3 Prof 1 studies.

3.3. Click on the Animation tab.


Click the Value Range button.

Enter a value of 0.25.

Click the Current frame only button.

Click OK

4. Ensure that only SC3 Flat Prof and SC3 Prof 1 studies are the only open studies.


6. Click on SC3 Flat Prof to activate it.

7. Click on Volumetric shrinkage result.


8.1. Ensure the plot properties for SC3 Flat Prof study are the same as the SC3 Prof 1 study, in particular the scale.

9. Click View Lock and choose All View, All Plots and All Animations.


• Watch how the shrinkage ranges appear and disappear on the part as the range plotted gets higher.


With the SC3 Prof 1 result, the volumetric shrinkage is more uniform across the part. The there is more of the part has the higher shrinkages. However, the shrinkage is not as uniform as it should be.

Table 30: Volumetric shrinkage range

Volumetric shrinkage Min MaxSC3 Flat Prof (from Table 26)SC3 Prof1


To display volumetric shrinkage as a probe plot

1. Click on SC3 Flat Prof to activate it.

2. Click the Probe XY plot to activate it.

• This will create the result in the SC3 Prof 1 study.


• Watch how the volumetric shrinkage changes and is more uniform in the SC3 Prof 1 study. At the end of packing, the 3 locations in the center of the part have very similar profiles. The probe at the end of fill has no change compared to the first packing analysis. To reduce its shrinkage, the packing pressure must be increased. The probe by the gate shows that the shrinkage went up, indicating the packing pressure decayed too quickly.

Determine the gate freeze time

To plot the Temperature result

1. Ensure only the Part layer is on.

2. Click on the SC3 Flat Prof study.

3. Click the Temperature plot.

• Since the plots are locked, the temperature results of SC3 Prof 1 will be configured like SC3 Flat Prof.

4. Click on the SC3 Prof 1 study.

5. Zoom up on the gate area so you can see the gate and surrounding area of the part.

6. Click (Step Backward) to animate the result one frame at a time to determine when the gate freezes.

Gate freeze interpretation

Due to the decay in the profile, the gate freezes faster then the first analysis with a constant pressure profile.

Pressure results

To plot pressure:XY

1. Click in the SC3 Flat Prof study to activate it.


• This will create the result in the SC3 Prof 1 study.

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Pressure results interpretation

Nodes 2681 and 1136 which represent areas closer to the gate have significantly been influenced by the profile. However, to make the volumetric shrinkage have a smaller range across the part, the pressure traces need to become closer. The decay needs to be faster, but not go to zero. It will drop then held at a pressure before decaying to zero. The pressure decay needs to be changed based on the nodes 2372, 40750 and the volumetric shrinkage probe plot.

Continue revising the packing profileContinue to revise the packing profile to reduce the shrinkage near the gate. The location of the profile knee and the decay to zero pressure after the knee will make a difference in the volumetric shrinkage by the gate.


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Competency check - Packing Optimization

1. If a part’s volumetric shrinkage is too high, what can be done to lower the volumetric shrinkage?

2. If the part has relatively low volumetric shrinkage near the gate. What can be done to increase the high shrinkage by the gate?


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Evaluation Sheet - Packing Optimization

1. If a part’s volumetric shrinkage is too high, what can be done to lower the volumetric shrinkage?

• Increasing the packing pressure is normally the best way to improve the volumetric shrinkage.

• Decreasing the injection time may also help in situations where the frozen layer fraction is rather high at the end of fill. A faster injection time will maintain a lower material viscosity and frozen layer fraction.

2. If the part has relatively low volumetric shrinkage near the gate. What can be done to increase the high shrinkage by the gate?

• The volumetric shrinkage drops after the packing pressure has dropped to knee and then decays down zero. Use the Volumetric Shrinkage path plot and pressure XY plot as a guide to adjust the packing profile. Small adjustments could make a huge difference.


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CHAPTER 5

Part Insert Overmolding

Aim

The aim of this chapter is to learn about part insert overmolding capabilities within Autodesk Moldflow Insight. You will also learn how to prepare the models, run an analysis and interpret the results for part insert overmolding projects.

Why do it

Autodesk Moldflow Insight has various capabilities regarding part insert overmolding analysis depending on the mesh type. This chapter will review the capabilities and describe how to use it.

Overview

In this chapter you will:

• Review the terms related to part insert overmolding and related technologies used in Moldflow.

• Review the part insert overmolding capabilities within Autodesk Moldflow Insight.

• Learn how to prepare models for part insert overmolding.

• Learn how to run an analysis with part inserts.

• Learn how to interpret results specific to part inserts.

Part Insert Overmolding 105

106 Chapter 5

Practice - Part insert overmolding

This chapter uses tetrahedral model for the practice and is described below.

Table 31: Model used for part insert overmolding

Description ModelConnector: starts on page 109

This part is an electrical connector and uses a tetrahedral mesh. The starting point will be a Dual Domain surface mesh. The Insert will be checked and corrected, then both parts will be meshed with tetrahedral elements. A Fill + Pack analysis will be run and the results will be reviewed.

Practice - Part insert overmolding 107

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Connector

For this connector, the following tasks will be done:

• Check the surface mesh on the insert and compare it to the connector.

• Fix the insert mesh.

• Mesh the fixed insert and connector with tetrahedral elements.

• Add the two meshes together.

• Assign the part insert properties.

• Run the analysis.

• Review the results.

Open projectThe project contains the necessary files for the connector.

To open a project

1. Click (File Open Project), and navigate to the folder My AMI 2010 Projects\AMI Standard 1\Overmolding and double click the project file Overmolding.mpi.






Reviewing the MeshThe two studies provided, Insert DD and Connector DD are surface (Dual Domain) meshes. They were created in Synergy using the same mesh settings. The part insert’s mesh must be compared with the connector’s mesh to determine if the elements perfectly match. If they don’t perfectly match, there may be some problems with converging in the solvers. The inserts mesh can be modified if necessary so it is a perfect match to the plastic part.

To prepare the connector study

1. Double click the Connector DD study to open it.

2. Click (File Save Study As) and enter the name Connector3D.


3. Change the name of the following layers by replacing New with Connector:

• New IGES.

• New Nodes.

• New Triangles.

4. Turn off all layers except Connector Triangles.

5. Rotate the model around as necessary to familiarize yourself with the part.


To prepare the insert study

1. Double click the Insert DD study to open it.

2. Click (File Save Study As) and enter the name Insert DD 1.

3. Change the name of the following layers by replacing New with Insert:

• New IGES.

• New Nodes.

• New Triangles.

4. Turn off all layers except Insert Triangles.

5. Highlight the Insert Triangle layer and click (Layer display) to change the color Triangular elements to red.

6. Highlight the Default layer, and click (Delete layer) to delete the layer.



The layer names and the color of the triangles were changed so the insert related layers and the connector related layers can be easily identified when the studies are added together.

To compare the insert’s mesh to the connector’s mesh

1. Activate the Connector 3D study.

2. Click (File Add) and select the Insert_dd_1.sdy file to add it to the Connector 3D Study.

3. Click (File Save Study As) and enter the name Connector w Insert.

4. Ensure that only the Connector triangles and Insert triangles layers are on.

110 Chapter 5

5. Set the Connector triangles layer to Transparent + Element Edges using the

display layer tool.

• This will make it easy to see the elements at the part - insert interface because the elements in this area will be a different color than the elements in the background.

6. Rotate the part to approximately -50 -15 -20.

7. Activate and move the cutting plane.

7.1. Click (Edit cutting planes).

7.2. Check the Plane XY box.

7.3. Click the Make active button.

7.4. Click and drag the left mouse button up to move the cutting plane in the positive Z-direction until the bottom plane of the insert is shown.

7.5. Uncheck the Show active plane box in the Move Cutting Plane dialog.

7.6. Click (Select) to close the Move cutting plane dialog.

8. Visually inspect the mesh.

• Rotate pan and zoom the model as necessary to see the insert and connector through the cutting plane.

• You should see that the elements of the insert do not match correctly with the elements of the connector. Turn off and on the Connector Triangles layer to help visualize the mismatch between the insert and connector.

• This difference in the mesh will create a solver warnings. The analysis will run, but may not be as accurate as possible. The warnings with the mesh will be fixed before the analysis is run.

9. Deactivate the cutting plane.



9.3. Click Close.

Fix the insert meshWhen the elements of the insert do not match with the plastic part, the insert can be fixed by using a copy of the plastic elements to recreate the portion of the part insert that is not correct.

3 When using Autodesk Moldflow Design Link, this matching problem will not occur. The following steps are done because Autodesk Moldflow Design Link was not used to prepare the mesh.


To delete the insert

1. Ensure the Connector w Insert study is active.

2. Highlight the following layers and click (Delete layer) to delete the following layers, in the order listed. Do NOT move the entities.

• Insert Iges.

• Insert Triangles.

• Insert Nodes.


The connector elements that touch the insert will be saved in a temporary study will all other elements being deleted. This temporary study will be used to create a corrected insert.

To create a temporary study of elements

1. Click (File Save Study As) and enter the name Connector Temp.

2. Delete the side elements.

2.1. Click (Front view) or manually enter the rotation 0, 0, 0 on the Viewpoint toolbar.

2.2. Band select the right, left, and top sides of the connector, as shown in Figure 32. Hold the Ctrl key to select all three regions at the same time. Make sure you don’t select any of the internal elements that touch the connector.

Figure 32: Band selecting the sides of the connector

2.3. Click the Delete key.

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3. Delete the top and bottom elements.

3.1. Click (Bottom view) or manually enter the rotation -90, 0, 0 on the Viewpoint toolbar.

3.2. Band select the top, and bottom of the connector, as shown in Figure 33. Hold the Ctrl key to select the two regions at the same time. Make sure you don’t select any of the internal elements that touch the connector.

Figure 33: Band selecting the top and bottom of the connector


4. Delete the bottom edge elements.

4.1. Click (Front view) or manually enter the rotation 0, 0, 0 on the Viewpoint toolbar.

4.2. Click (Enclosed items only) on the Selection toolbar.

4.3. Zoom up on the bottom edge of the remaining elements.

4.4. Band select around the bottom edge elements, ensuring you don’t enclose any elements normal to the screen.

Figure 34: Band selecting the front edge elements


5. Click (Mesh Mesh Tools Nodal Tools Purge Nodes).

5.1. Click Apply.

5.2. Click Close.

6. Delete the Connector IGES layer.


The surface mesh of the plastic part that touches the insert has now been isolated into a separate study. Now this can be added to the insert, the elements of the insert that need to be replaced can be and the new insert mesh can be properly connected.


To combine the temporary study with the insert study

1. Open the Insert DD 1 study.

2. Click (File Add) and select the connector_temp.sdy file.

You should see where the elements overlap and where the insert elements are not touching the added connector elements, as shown in Figure 35. The insert elements that are overlapping the connector elements will be deleted.

Figure 35: Insert with the touching connector elements overlapping

To move the good insert elements to a new layer

The insert elements that are not overlapping the connector elements will be moved to a new layer to isolate them.

1. Click (Front view) or manually enter the rotation 0, 0, 0 on the Viewpoint toolbar.

2. Click (Enclosed items only) on the Selection toolbar.

3. Band select the insert elements outside the connector elements. To select them all the band must go just above the intersection with the connector elements. Figure 36 shows the band selection around one of the insert’s fingers for clarity. All the elements outside the connector elements must be selected.

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Figure 36: Insert elements not touching the connector elements are selected

4. Click (New layer) called Keep.

5. Click (Assign) the selected insert elements to the layer Keep.

To delete unwanted elements

1. Turn on the Insert Triangles layer and off all other layers.

2. Select all the triangles on the Insert Triangles layer.

3. Click the Delete key.

4. Turn on the Connector Triangles and Keep layers.

5. Select all of the displayed triangles and assign them to the Insert Triangles layer.

6. Click (Mesh Mesh Tools Nodal Tools Purge Nodes).

6.1. Click Apply.

6.2. Click Close.

To repair the holes

1. Turn on the Insert Nodes and Connector Nodes layers.

2. Use (Create triangles) to make elements to fill in the sides of the fingers, as shown in Figure 37. There are eight places this needs to be done.


Figure 37: Create side elements

3. Use (Fill hole) to create the elements on the top and bottom faces of the insert, as shown in Figure 38. There are eight places this needs to be done.

Figure 38: Fill hole on the fingers

4. Use (Merge nodes) to remove smaller elements as shown in Figure 39. Be sure to keep the node on the straight line at the edge of the connector.There are 16 places this needs to be done.

Figure 39: Merge nodes

5. Click (Mesh Orient All) to ensure the mesh orientation is correct.

6. Click (Mesh Statistics) to ensure all mesh related problems are fixed.

6.1. Fix any problems that are detected by the Mesh Statistics.

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To finish organizing the study

1. Click (Select by properties) or type CTRL + B.

2. Click OK to select nodes.

3. Click (Assign to layer) all the nodes to the Insert Nodes layer.

4. Turn off all the nodes layers.

5. Select all the triangles and assign them to the Insert Triangles layer.

6. Click (Clean Layer) to remove all layers without entities.

7. Click (Edit Remove Unused properties).


Mesh the fixed insert and connector with tetrahedral elementsNow that the insert’s mesh will match the connector’s mesh, both parts will be meshed with tetrahedral elements.

To create a tetrahedral mesh for the insert

1. Click (File Save Study as), and name the insert Insert 3D.

2. Right click (Dual Domain mesh) in the study tasks list and select Set Mesh Type 3D.

3. Mesh the insert.

3.1. Click (Mesh Generate Mesh).

3.2. Click the Tetra Refinement tab.

3.3. Set the Minimum number of elements through thickness to 4.

3.4. Click Mesh Now.

4. Click (Mesh Mesh Repair Wizard).

4.1. Step through the wizard and correct any problems identified with the wizard’s default settings.


5. Cleanup the model.

5.1. Turn on all the layers except the Insert IGES layer.

5.2. Click (Select by properties) or type CTRL + B.

5.3. Click OK to select nodes.

5.4. Assign all the nodes to the Insert Nodes layer.

5.5. Turn off the Insert Nodes layer.

5.6. Select all the Tetrahedral elements and assign them to the Insert Triangles layer.

5.7. Rename the Insert Triangles layer to Insert Tetras.

5.8. Highlight the Insert tetras layer and click (Layer display) to change the color of tetrahedral elements on the Insert Tetras layer to orange.

5.9. Click (Clean Layer) to remove all layers without entities.

There should only be 3 layers remaining.

5.10.Click (Edit Remove Unused properties).


To mesh the connector with tetrahedral elements

1. Activate the Connector Temp study.

2. Close the study.

3. Open the Connector 3D study.


5. Mesh the insert

5.1. Click (Mesh Generate Mesh).


5.3. Ensure the Minimum number of elements through thickness is set to 6.




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7.1. Turn on all the layers except the Default Layer and Connector IGES layer.

7.2. Click (Select by properties) or type CTRL + B.


7.4. Assign all the nodes to the Connector Nodes layer.

7.5. Turn off the Connector Nodes layer.

7.6. Select all the Tetrahedral elements and assign them to the New Tetras layer.

7.7. Rename the New Tetras layer to Connector Tetras.



7.9. Click (Edit Remove Unused properties).


Add the two meshes togetherNow there should be Dual Domain versions of the connector and Insert, plus tetrahedral mesh versions. The final study will combine the tetrahedral meshes together to make the study used for analysis.

To combine the studies

1. Open the Connector 3D, if not already open.

2. Click (File Add) and select the study Insert 3D.

3. Activate and move the cutting plane.

• The mesh is checked to ensure it matches.




3.4. Click and drag the left mouse button up to move the cutting plane in the positive Z-direction until the bottom plane of the insert is shown.

3.5. Uncheck the Show active plane box.

3.6. Click (Select) to close the Move cutting plane dialog.


4. Visually inspect the mesh.

• Rotate pan and zoom the model as necessary to see the insert and connector through the cutting plane.

• You should see that the elements of the insert now match correctly with the elements of the connector.




5.3. Click Close.


Assign the part insert propertiesThe elements that represent the part insert have the same properties as a plastic part. The properties must be set for the insert.

To set the part insert properties

1. Turn off all layers except the Insert Tetras layer.

2. Select all the elements.

3. Click (Edit Change Property Type).

4. Select Part insert (3D) and click OK.

5. Click (Edit Properties).

5.1. Ensure Metal is the material chosen and click the Select button to set the material.

5.2. Click the Select button to pick a mold material.

5.3. Select Moldmax HH as the material and hit the select button.

5.4. Click OK on the Select material dialog.

5.5. Set the Local heat transfer coefficients to Perfect contact.

5.6. Ensure the Initial temperature is 25ºC.

5.7. Set the name as BeCu Insert.

6. Click OK.


8. Turn on the Connector Tetras layer


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Run the analysisAnalysis parameters for the connector will be set up and the analysis will be run.

To run the analysis

1. Close all open studies except the Connector 3D study.

2. Set the analysis sequence.

2.1. Double-click (Analysis Sequence) in the Study Tasks pane.

2.2. Select the Fill + Pack analysis sequence.

2.3. Click OK.

3. Select the material as SABIC Innovative Plastics US, LLC, Valox 364.

4. Set the injection location on the center node at the end of the runner as shown in Figure 40.

Figure 40: Injection locations for the connector


Table 32: Connector analysis parameters

Parameter ValueMold Temperature 60º CMelt Temperature 250º CFilling control Injection timeFill time 0.6 secondsVelocity/pressure switch-over AutomaticPack/holding control %Filling pressure vs timePacking profile 0.2

50.8

80800

Cooling time 6 seconds


6. Double-click (Start analysis).

• The analysis will take about a half an hour to an hour to run.

• A study with results is available so you don’t have to wait for results.

Review the resultsThe results to be reviewed are going to concentrate on the results that are influenced by the insert. The first task will read in results from an analysis that was done for you ahead of time. Use these results if you can’t wait for your analysis to finish.

To read in results already run

1. Consider using the Job Manager to abort the analysis you are running on this part.

2. Double-click the Connector 3D Pre-Run study to open the study with results already run.

To plot temperature

1. Click the Temperature result.



Ensure Shaded is selected.

2.2. Click the Mesh Display Tab.

Ensure the Element surface display is Transparent.

2.3. Click the Optional Setting tab.

Ensure the Color is set to Smooth.

2.4. Click OK.

3. Rotate the part to approximately -50 -15 -20

4. Click (Step forward) to the first time step.

Advanced Options Solver Parameters Flow Analysis

Intermediate results:• 7 filling phase• 6 packing phase• 3 cooling phaseSolver parameters:• Gate contact diameter - Specified

• Gate diameter - 5 mm

Advanced Options Solver Parameters Core Shift Uncheck Perform core shift analysis

Table 32: Connector analysis parameters

Parameter Value

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5. Click (Results Examine result). Click on the following locations:

• Portion of part already filled.

• Insert not in the part.

• Insert in the part.

You can see the influence of the mold temperature on the part and insert as these temperatures are the mold temperature of ~60ºC. The initial temperature of the insert can also be seen as it is 25ºC.

To plot a temperature probe XY plot


1.1. Click the Temperature as the new result.

1.2. Click Probe XY plot as the Plot type.

1.3. Click the Properties tab, then the XY Plot Properties(2) tab.

1.4. Enter the Y range manually from 25ºC to 300ºC.

1.5. Click OK

2. Click on the three locations shown in Figure 41, in the full wall thickness, on the plastic part above the insert, and on the insert not in the plastic.

3. Click (Select) to stop picking curves.

Figure 41: Temperature probe locations


Notice how the temperature of the insert and mold are also seen in this result.

/ Other methods of displaying temperature results could be handy. With the probe plot, many cross-sections can be defined at one time to look at the temperature distribution through the thickness of the part as a shaded image at many locations at once.


To plot Fill time








Ensure the Color is set to banded.

2.4. Click OK.


4. Zoom in and pan on the result to see the filling pattern.

Notice how the filling is influenced by the insert. There is significant hesitation due to the thickness of the insert and it is not even on the top and bottom of the insert.

To plot Pressure at V/P switchover

1. Click the Pressure at V/P switchover result.








2.4. Click OK.


The pressure highlights the same thing as the fill time, the insert significantly influences the filling. Here the last place to fill is over the insert.

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To plot Velocity

1. Click the Velocity result.



Ensure Vector as darts is selected.


Set the Min to 0 and Max to 50 cm/s.

Ensure the Extended color box is checked.



2.4. Click OK.


Notice how the material races around the thick area of the part.

To plot Volumetric shrinkage




Set the Min to 6.5 and Max to 13%.





Set the Animate result over to Single data set.

Set the Animate result at the last time in the combo box list.

Set the Value range to 0.5.

Click Current frame only.

2.4. Click OK.


Notice how the volumetric shrinkage over and under the insert is only about half of the shrinkage in the main wall of the part.


SummaryWhen modeling part inserts, the mesh of the insert must match the mesh of the part. The initial temperature of insert can be set. How the insert influences the filling of the part can easily be seen.

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CHAPTER 6

Two-Shot Sequential Overmolding

Aim

The aim of this chapter is to learn about two-shot sequential overmolding capabilities within MPI. You will also learn how to prepare the models, run an analysis and interpret the results for two-shot sequential overmolding projects.

Why do it

MPI has various capabilities regarding two-shot sequential overmolding analysis depending on the mesh type. This chapter will review the capabilities and describe how to use this capability.

Overview

In this chapter you will:

• Review the terms related to two-shot sequential overmolding and related technologies used in Moldflow.

• Review the two-shot sequential overmolding capabilities within MPI.

• Learn how to prepare models for two-shot sequential overmolding.

• Learn how to run a two-shot sequential overmolding analysis.

• Learn how to interpret results specific to two-shot sequential overmolding.

Two-Shot Sequential Overmolding 127

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Practice - Two-Shot Sequential Overmolding

This chapter uses several models for the practice and are described below. One is a Dual Domain mesh and the other uses a tetrahedral mesh. Do the practice for the model of the mesh type you use most. Analyze the other as time permits.

Table 33: Models used for two-shot sequential overmolding

Description ModelBox with window: starts on page 131

This part uses a Dual Domain mesh. The box is molded first with Nylon, then the window is molded second with polycarbonate. Use this part if your primary mesh type you use is midplane or Dual Domain.

Moldflow Logo: starts on page 139

This part is plaque with the Moldflow logo molded into it. This part uses a tetrahedral mesh. The starting point will be a Dual Domain surface mesh. The second shot will be checked and corrected, then both parts will be meshed with tetrahedral elements. A Fill + Pack analysis will be run and the results will be reviewed.

Practice - Two-Shot Sequential Overmolding 129

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Box with window

For this box and window, the following tasks will be done:


• Set the analysis type.

• Assign the second shot properties.




To open a project

1. Click (File Open Project), and navigate to the folder My AMI 2010 Projects\AMI Standard 1\TwoShot and double click the project file TwoShot.mpi.






Reviewing the MeshThe two studies provided, Box DD and Window DD are surface (Dual Domain) meshes. The window was created from elements of the box and the fill hole tool so the elements will match up. If they don’t perfectly match, there may be some problems with converging in the solvers. To practice using Moldflow to step through the problem of viewing and fixing meshes that are not matched Refer to the Moldflow logo practice for information on repairing meshes that are not perfectly matched.

To prepare the connector study

1. Double click the Box DD study to open it.

2. Click (File Save Study As) and enter the name Box1.

3. Click twice on a layer to change the name of the following layers by replacing New with Box:

• New IGES Surface.

• New Triangles.

• New Nodes.

• New Runners


4. Turn off all layers except Box Triangles.



To prepare the Window study

1. Double click the Window DD study to open it.

2. Click (File Save Study As) and enter the name Window1.

3. Change the name of the following layers by replacing New with Window:

• New Triangles.

• New Nodes.

• New Runners.

4. Turn off all layers except Window Triangles.

5. Click (Layer Display) to change the color Triangular elements on the Window Triangle layer to yellow.



The layer names and the color of the triangles were changed so the window related layers and the box related layers can be easily identified when the studies are added together.

Add the two meshes togetherNow there should be Dual Domain versions of the box and window. These studies will be combined to make a final study to be used for analysis.


1. Activate the Box1 study.

2. Click (File Save Study As) and enter the name Box & Window1.

3. Click (File Add) and select the window1.sdy file.

4. Highlight the Box Triangles layer.

5. Click (Layer Display) to change the color Triangular elements on the Box Triangle layer to red.


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Set the analysis typeThe molding process and element properties must be set so a two-shot (overmolding) analysis can be run.

To set the molding process

1. Click Analysis Set Molding Process Thermoplastics Overmolding.

• With the molding process set, the proper element properties can now be set.

Assign the second shot propertiesThe elements that represent the second shot, part and feed system Must have their properties modified to represent the second shot.

To set the part properties to 2nd shot

1. Turn off all layers except the Box Triangles layer.



4. Select all the properties in the Select Properties dialog.

5. Click the Overmolding Component tab.

6. Select 2nd shot as the component.

7. Click OK.

To set the feed system properties to 2nd shot

1. Turn off all layers except the Box Runners layer.

2. Change the runner.

2.1. Select a runner element.


3.1. Click the Overmolding Component tab.

3.2. Select 2nd shot as the component.

3.3. Ensure the Apply to all entities that share this property is checked.

3.4. Click OK.

4. Change the gate.

4.1. Select a gate element.



5.1. Click the Overmolding Component tab.

5.2. Select 2nd shot as the component.

5.3. Ensure the Apply to all entities that share this property is checked.

5.4. Click OK.

6. Delete the yellow injection location symbol at the end of the runner.



The color of the runner and gate turned from green to beige because the default color for the entities is defined for the layer. This allows you to easily distinguish the runners from the first shot and the second shot.

Run the analysisAnalysis parameters for the Box & Window will be set up and the analysis will be run.

To run the analysis

1. Close all open studies except the Box & Window1 study.


2.1. Double-click the Analysis Sequence icon in the Study Tasks pane.

2.2. Select the Fill + Pack + Overmolding Fill + Overmolding Pack analysis sequence.

2.3. Click OK.

3. Set the materials.

3.1. Click (Material A) to select the first shot material to SABIC Innovative Plastics US, LLC, Lexan HF1110.

3.2. Click (Material B) to select the second shot material to BASF, Ultramid A3L HP.

4. Click (Overmolding injection location) to set the injection location at the end of the second shot runner.

5. Double-click the Process Settings icon and enter the parameters shown in Table 34.

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• The analysis will take about 30 to 45 minutes to run.


Table 34: Box and Window analysis parameters

Parameter ValueFlow Settings for First Component Stage - Page 1 of 2

Mold Temperature 100º CMelt Temperature 300º CFilling control Flow rateFlow rate 3.4 cm3/sec.Velocity/pressure switch-over AutomaticPack/holding control %Filling pressure vs timePacking profile .1

30.5

1001000

Cooling time 4 secondsAdvanced options Solver parameters (edit) Intermediate Output tab

Filling phase, Profiled result 20Packing phase, Profiled result 20

Flow Settings for Overmolding Component Stage - Page 2 of 2

Mold Temperature 100º CMelt Temperature 300º CFilling control Flow rateFlow rate 20.13 cm3/sec.Velocity/pressure switch-over AutomaticPack/holding control %Filling pressure vs timePacking profile .1

30.5

1001000


3 The parameters set up were determined by preliminary analysis, including the mold temperature, melt temperatures, flow rates, packing profiles and cooling time. The analysis was set up so the cycle time for each component is the same.


Review the resultsThe overmolded part has all the same results as does the first shot and a typical flow analysis. The temperature (intermediate profiled) result will be the only specific result viewed. Look at other results as you would like to see the influence if you can see an influence of the overmolding. The analysis has been done for you. Use these results if you can’t wait for your analysis to finish.



2. Double-click the Box & Window Pre-Run study to open the study with results already run.

To plot temperature


1.1. Click the Temperature (Overmolding) result in the available results list.

1.2. Click the XY plot as the plot type.

1.3. Click the Plot Properties tab.

1.4. Select Normalized thickness as the Independent variable.

1.5. Click the XY Plot Properties (2) tab.

1.6. Set the Y range to Manual with a Min value of 100 and Max of 300.

1.7. Click OK.

2. Set up the part for picking triangles.

2.1. Ensure that only the following layers are on and the rest are off:

Box Triangles.

Window Triangles.

Window Runners.

2.2. Click the Back view button to rotate the part to 0, 180, 0.

2.3. Pan and zoom to the left side of the part near the runner for shot 2, as shown in Figure 42.

3. Pick two triangles on the part referring to Figure 42.

• The first is on the nominal wall below the runner and to the left of the window.

• The second is on the thin rim where the box and window overlap.

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Figure 42: First two nodes picked on the box

4. Set up the part for picking two more triangles.

4.1. Click the Front view button to rotate the part to 0, 0, 0.

4.2. Pan and zoom to the right side of the part near the triangles already picked.

5. Pick two more triangles on the part referring to Figure 42.

• The first is directly over the red marker on the thin rim.

• The second is on the nominal wall of the window.

Figure 43: Second two nodes picked on the window

6. Click (Select) when done picking triangles to prevent from picking any more triangles.

7. Click (Animate result.). Start by looping through the cycle several times then one frame at a time.


The triangles were picked so the -1.0 value of the red and blue markers represent the same location in the part, the box/window interface. You can see by the red data point, that the second shot heats up the mold surface of the first shot. The blue data point shows the second shot is also hotter on the side with the first shot than the steel mold on the other side of the cross section.

To view other results for the overmolded part

1. Click on other results from the overmolding. Interesting results may be:

• Pressure.

• Pressure at injection location: XY plot.

• Fill time.

• Temperature at flow front.

• Shear rate bulk.

• Bulk temperature.

• Frozen layer fraction.

• Shear stress at wall.

• Volumetric shrinkage at ejection.

Determine how the overmolding influences these results.

SummaryTo create run a two-shot analysis, the molding process must change to Thermoplastics Overmolding. The elements in the second shot must be defined as the second shot in its properties. The first and second shot materials must be set. The mold temperature and cycle times must be the same. The first shot insolates to some degree the flow front where the first shot and second shot overlap.

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Moldflow logo

For the, the following tasks will be done:

• Review the mesh.

• Fix the second shot mesh match.

• Mesh the fixed second shot and the first shot with tetrahedral elements.


• Assign the Overmolded component properties.




To open a project

1. Click (File Open Project), and navigate to the folder My AMI 2010 Projects\AMI Standard 1\TwoShot and double click the project file TwoShot.mpi.






Reviewing the MeshThe two studies provided, Back DD and Logo DD are surface (Dual Domain) meshes. They were created in Synergy using the same mesh settings. The logo’s mesh must be compared with the Back’s mesh to determine if the elements perfectly match. If they don’t perfectly match, there may be some problems with converging in the solvers. The inserts mesh can be modified if necessary so it is a perfect match to the plastic part.

To look at the match, the meshes can be visually inspected, or checks in the solver can be used to find any problems. By using visual inspection, the exact location of problems can be found, however, it can be time consuming. Using the solvers will indicate problems, but not where the problems are. For this part, the solvers will be used to find problem areas. To save time, a study has been created with a tetrahedral mesh of the two shots with an analysis run so the warning messages can be found in the analysis log.

/ Autodesk Moldflow Design Link and higher has the capability to mesh assemblies that will ensure the boundary between components is properly meshed, preventing solver errors.


To determine if the part has mesh matching problems

1. Open the study MF Logo & Back Test Match.

• The study contains a tetrahedral mesh of the two parts, the logo and the back, the analysis sequence including overmolding and the injection locations are set. The analysis will be started and all that we a looking for are warnings.


3. Click on the Overmolding Fill+pack-Check tab in the log files area.

• Look for warnings like the one shown in Figure 44.

• There will be nothing in this area until the checking of the model has begun and found an error.

Figure 44: Warnings on an overmolded part with mesh matching problems

4. Click (Job Manager). One way is to do this is to press CTRL + J.

5. Watch the Priority Jobs Queue.

• You should see that the analysis is checking the model, first the flow, then the Overmolding. Chances are that by the time the Job Manager was opened, the overmolding checking is in progress.

6. Abort the analysis when checking the model is complete.

• A message will appear indicating the checking is complete.

6.1. Highlight the Fill + Pack analysis in the priority queue.

6.2. Click (Abort).

6.3. Close the Job Manager.

7. Close the study.

Fixing the MeshYou found that the mesh has matching errors. The mesh will be fixed following the tasks below by modifying the Dual Domain meshes then re-creating the tetrahedral mesh. The elements of the Back study that forms the hole for the logo will be added to the study of the Logo and the meshes will then be connected.

** WARNING 301200 **3D Part elements are not matching the overmolded elements at the overmolded interfaces. Could

affect solver convergence.

** WARNING 301210 **Nodes from the 3D part or overmolded tetrahedronelements are either inside its opposingtetrahedron element or a significant distancefrom it. The overmolding and part elements arenot matching up very well at the interface.

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To isolate elements of the Back study forming the logo pocket

1. Double click the MF Back DD study to open it.

2. Click (File Save Study As) and enter the name Back DD to logo.

3. Delete the top and bottom elements by:

3.1. Click (Enclosed Items Only) on the selection tool bar.

3.2. Enter a rotation of -90, -90, in the viewpoint tool bar.

3.3. Click and band select the elements on the top and bottom faces of the part, as shown in Figure 45.

Figure 45: Selecting the top and bottom faces

3.4. Rotate the part to ensure you only have elements on the top and bottom faces selected.

3.5. Click (Delete) or the Delete key on the keyboard.

The remaining elements include the outside edges of the part and the elements that form the logo pocket.

4. Delete the edge elements by:

4.1. Click the Front View icon to rotate the part to 0, 0, 0.

4.2. Hold the CTRL key and band select the elements forming the outside edges, in several steps ensuring you don’t select the logo pocket.

4.3. Click (Delete).

The only remaining elements are the elements forming the logo pocket.


5. Clean up the model by:

5.1. Click (Mesh Mesh Tools Nodal Tools Purge Nodes).

Click Apply.

Click Close.

5.2. Highlight the IGES Surface click (Delete layer). Do not move entities to the active layer.

5.3. Click (Clean Layers).

5.4. Change the name of the following layers to:

Fix Nodes.

Fix Triangles.

5.5. Turn off all layers except Fix Triangles.

6. Click (File Save Study)

7. Close the study.

To delete the elements of the logo that are not needed

1. Double click the MF Logo DD study to open it.

2. Click (File Save Study As) and enter the name MF Logo fixed.

3. Deselect the Enclosed Items Only icon on the selection tool bar.

4. Enter a rotation of -90, -90, in the viewpoint tool bar.

5. Band select the elements in the middle of the part, as shown in Figure 46.

Figure 46: Selecting the logo elements to delete

6. Click (Delete).

The remaining elements include the top of the logo and the end of the two pins.

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7. Clean up the model by:

7.1. Click (Mesh Mesh Tools Nodal Tools Purge Nodes).

Click Apply.

Click Close.

7.2. Click (Clean Layers).

7.3. Turn off all layers except New Triangles.


To add the temporary studies together

1. Ensure the MF Logo Fixed study is open.


2.1. Ensure Default to project directory is checked on the General tab.

2.2. Click OK.

3. Click (File Add).

4. Select the back_to_logo.sdy file.

5. Click Open.

To connect the meshes that were added together

The meshes have been added together, but they are not connected. The free edges diagnostic is used to show the problem.

1. Click (Mesh Mesh Diagnostics Free Edges Diagnostic).

1.1. Click Show.

• Notice how the entire parameter of the logo is not connected between the top and sides. The free edges will be automatically stitched.

2. Turn on all node layers.

3. Click (Mesh Mesh Tools Edge Tools Stitch Free Edges).

4. Band select the entire part or type CTRL + A.

5. Click Apply.

• All the free edges should now be fixed.

6. Click Close.

7. Turn off all node layers.


To find and fix the mesh orientation problem

1. Click (Mesh Mesh Statistics).

• Notice that the only problem now is the mesh orientation.

1.1. Click Close on the Mesh Statistics dialog.

2. Click (Mesh Mesh Diagnostics Orientation Diagnostic).

2.1. Click Show.

2.2. Click Close.

3. Click Mesh Orient All.

• The mesh should not be correct with all elements being blue.

4. Click Mesh Show Diagnostic to toggle off the orientation diagnostic.


Mesh shot one and two with tetrahedral elementsNow that the logo’s mesh matches the back’s mesh, both parts will be meshed with tetrahedral elements.

To create a tetrahedral mesh for the logo

1. Click (File Save Study As) and name the study MF Logo 3D.


3. Mesh the logo

3.1. Click (Mesh Generate mesh).






144 Chapter 6

5. Organize the nodes.

5.1. Turn on all the layers except the IGES Surface layer.

5.2. Rename the IGES Surface layer to Logo IGES Surface.

5.3. Click (Edit Select by Properties) or type CTRL + B.


5.5. Assign all the nodes to a New Nodes layer.

5.6. Change the name of that New Nodes layer to Logo Nodes.

5.7. Turn off the Logo Nodes layer.

6. Organize the tetras


6.2. Rename the New Tetras layer to Logo Tetras.

6.3. Change the color of tetrahedral elements on the Logo Tetras layer to Yellow.





To create a tetrahedral mesh for the back

1. Double click the MF Back DD study to open it.

2. Click (File Save Study As) and name the study MF Back 3D.


4. Mesh the back.

4.1. Click (Mesh Generate mesh).








6.1. Turn on all the layers except the Default Layer and IGES Surface layer.

6.2. Rename the IGES Surface layer to Back IGES Surface.

6.3. Click the Select by icon or type CTRL + B.


6.5. Assign all the nodes to a New Nodes layer.

6.6. Rename that New Nodes layer to Back Nodes.

6.7. Turn off the Back Nodes layer.


6.9. Rename the New Tetras layer to Back Tetras.

6.10.Click the Clean Layer icon to remove all layers without entities.


6.11.Click (Edit Remove Unused properties).


Add the two meshes togetherNow there should a tetrahedral mesh version for both the back and logo. The final study will combine the tetrahedral meshes together to make the study used for analysis.


1. Open the MF Back 3D study, if not already open.

2. Click (File Save Study As) and enter the name MFBack&Logo.

3. Click (File Add) and select the study MF Logo 3D.

4. Right-click on the Logo Tetras layer and move it up in the list so it is just below the Back Tetras layer.


Assign the second shot propertiesCurrently, the molding process is thermoplastics injection molding therefore the overmolding second component properties can’t be set. Both the molding process and properties must be set.

146 Chapter 6

To set the molding process

1. Click Analysis Set Molding Process Thermoplastics Overmolding.

To set the Logo’s properties

1. Turn off all layers except the Logo Tetras layer.


3. Click (Edit Change Property Type).

4. Select Overmolding second component (3D) and click OK.


6. Turn on the Back Tetras layer.


Run the analysisAnalysis parameters for the Back and Logo will be set up and the analysis will be run.

To run the analysis

1. Close all open studies except the MFBack&Logo study.


2.1. Double-click (Analysis Sequence) in the Study Tasks pane.

2.2. Select the Fill + Pack + Overmolding Fill + Overmolding Pack analysis sequence.

2.3. Click OK.

3. Set the materials.

3.1. Click (Material A) and set the first shot material to DuPont Engineering Polymers (Moldflow Verified), Zytel 101F NC010.

3.2. Click (Material B) and set the second shot material to Advanced Elastomer Systems, Santoprene 121-50 M100.


4. Set the injection locations.

4.1. Rotate the model to 130, 45, 30.

4.2. Click (Injection Location) to set the injection location for the Back at the location as shown in Figure 47.

4.3. Click (Overmolding injection locations) to set the injection location for the Logo, on the end of the post that is attached to the underside of the M in Moldflow, as shown in Figure 48.


Table 35:

Figure 47: Injection location for the back Figure 48: Injection location for the

logo


Parameter ValueFlow Settings for First Component Stage - Page 1 of 2

Mold Temperature 50º CMelt Temperature 295º CFilling control Injection timeInjection time 1 SecondVelocity/pressure switch-over AutomaticPack/holding control %Filling pressure vs timePacking profile 0

108080


148 Chapter 6


• The analysis will take about an hour to run.


Review the resultsThe results to be reviewed are mainly going to concentrate on the results of the overmolding (second shot) that are influenced by the first shot. The first task will read in results from an analysis that was done for you ahead of time. Use these results if you can’t wait for your analysis to finish.



2. Double-click MF Back & Logo Pre-Run to open the study with results already run.

To plot temperature

1. Click the Temperature (3D overmolding) result.

2. Highlight the second shot material in the database and find the ejection temperature.

• The ejection temperature for second shot material is _________

Advanced options Solver parameters (edit) Intermediate Results Edit intervals button

Filling phase, 5Packing phase, 10Cooling phase, 5

Flow Settings for Overmolding Component Stage - Page 2 of 2

Mold Temperature 50º CMelt Temperature 200º CFilling control Injection timeInjection time 1 SecondVelocity/pressure switch-over By % volume filled, 99%Pack/holding control %Filling pressure vs timePacking profile 1

81

1201200


3 The parameters set up were determined by preliminary analysis, including the mold temperature, melt temperatures, injection times, packing profiles and cooling time. The analysis was set up so the cycle time for each component is the same.


Parameter Value


3. Activate the cutting plane.


3.2. Check the Plane ZX box.


3.4. Click the Flip button.

3.5. Click Close.

3.6. Rotate the part and zoom as necessary you can see the part on the cutting plane.

• Notice how the results are displayed on both the first and second shots.



Ensure the To field is set to the maximum value.

Ensure the Animate result over field is TIme.


Ensure All frames is selected.

4.3. Click OK.

5. Rotate the part to approximately -50 -15 -20


7. Stop the animation at a time that interests you.

8. Click (Results Examine result). Click on the following locations:

• On the cutting plane of the first shot.

• On the cutting plane of the second shot.



9.2. Uncheck the Plane ZX box.

9.3. Click Close.

The temperature of much of the first shot is above the ejection temperature of the second shot material. This is significantly slowing down the cycle time.

Possibly a more efficient way to look at the results is to use a probe plot. This is done next.

To plot a temperature (3D overmolding) probe XY plot


2. Click the Temperature (overmolding) as the new result.

150 Chapter 6

3. Click Probe XY plot as the Plot type.

4. Click the Properties tab, then the XY Plot Properties(2) tab.

5. Enter the Y range manually from 70ºC to 310ºC.

6. Click OK

7. Click the Back View icon .

8. Ensure that both the Back Tetras and Logo Tetras layers are on. Zoom in on the gate and pick on the back of the part under the logo as shown in Figure 49.

Figure 49: First temperature probe plot location

9. Click the Front View icon .

10. Pick directly over the first location picked, then pick in the nominal wall as show in Figure 50.

• By picking the same location once from the back view and the second from the front view, the data points represent the back and logo at the same location with the highest X value on the XY graph being the same location in space.

Figure 50: Second and third probe plot locations.

11. Click (Select) to stop picking locations to plot.



The plot clearly shows how the second shot heats up the first shot and how the first shot delays the cooling of the second shot.

To plot Fill time on the back


2. Click Results Plot Properties.







2.4. Click OK.


4. Zoom in and rotate on the result to see the filling pattern.

The filling of the back does not indicate any problems. There is a very small amount of hesitation due to the pocket for the logo, but nothing needs to be done with it.

To plot Velocity on the logo

1. Click the Velocity (overmolding) result.

2. Click Results Plot Properties.


Ensure Vector as darts is selected.


Set the To combo box to about 2s.


Set the Min to 0 and Max to 100 cm/s.




2.5. Click OK.


Notice how the material races through the part in the shortest path possible.

/ Other methods of displaying temperature results could be handy. With the probe plot, many cross-sections can be defined at one time to look at the temperature distribution through the thickness of the part as a shaded image at many locations at once.

152 Chapter 6

To plot Volumetric shrinkage

1. Click (Vertical Split).

2. Turn on the locks.

2.1. Click (View Lock All Views).

2.2. Click (View Lock All Animations).

3. Click in the left window.


5. Click in the right window.

6. Click the Volumetric shrinkage (overmolding) result.



Set the Min to 3 and Max to 19%.





Set the Animate result over to Single data set.

Set the Animate result at the last time in the combo box list.

Set the Value range to 1.

Click Current frame only.

7.4. Click OK.

7.5. Set the same plot properties for the other result.


Notice how the volumetric shrinkage for the back is considerably higher than it is for the logo. What consequences are there due to that shrinkage difference?.

SummaryThe temperature of the first shot has a significant influence on the temperature and heat transfer of the second shot.


154 Chapter 6

CHAPTER 7

Design of Experiments (DOE) Analysis

Aim

The aim of this chapter is to review the theory, setup, and interpretation of results for Design of Experiments (DOE) analysis.

Why do it

A DOE analysis will provide you with information about the sensitivity of input parameters about a given part design. The DOE analysis can identify solutions an engineer may not have considered, and can assist the engineer to improve the part quality, by relating physical inputs to physical outputs in a real-time intuitive way.

Consider a very simple case; where a new tool needs to be set up. The possible input parameters that affect the setup include:

The total number or parameters will easily exceed 10. However, experimenting with 10 parameters is very impractical.

The typical way a new part is set up is to use a mid-range condition and see how the part behaves. Depending on what results this first run generates, the engineer makes some changes, based on their experience and observations of the new results. This is typically the beginning of a lengthy trial-and-error process.

Instead of applying this trial-and-error approach, the engineer should first apply a screening experiment. This experiment will separate the most critical parameters for the part quality and rate them in order of their importance.

As a next step, the engineer should deploy a detailed full factorial experiment, where the analysis takes these parameters and shows all possible interrelations between them and the part quality.

• Injection pressure. • Cooling time.• Melt temperature. • Gate freeze time.• Mold temperature. • Cycle time.• Injection speed. • Many others.

Design of Experiments (DOE) Analysis 155

Overview

You will use two parts with a DOE analysis. One you will use to practice setting up the analysis. A second part has the DOE analysis done for you. For this part, you will review the results and determine what inputs have the most influence on volumetric shrinkage variation.

156 Chapter 7

Practice - Design of Experiments (DOE) Analysis

This chapter has two models used with DOE and are described below. You will work on both models.

Table 37: Models used with a DOE analysis

Description ModelPlate: starts on page 158

You will use the Plate model to practice setting up and running a DOE. The model has a very small number of elements so the run time will be short. The plate is 100 mm x 300 mm and has a nominal 2.5 mm thick with a 1.5 mm section in the center.

Cap: starts on page 160

For the Cap model, determine what is the dominant factor that has the greatest effect on volumetric shrinkage variation. To save time the DOE analysis has been run on the cap for you.

Practice - Design of Experiments (DOE) Analysis 157

Plate

For the plate study, a DOE analysis will be set up and run. It is very small so it will not take long to run.

Setup

To open a project

1. Click (File Open Project) and navigate to the folder My AMI 2010 Projects\AMI Standard 1\DOE.

2. Double click the project file DOE.mpi.

3. Click File Preferences and ensure that System Units are set to Metric.






To review the model

1. Open the model plate.



Running a DOE analysis

To set the analysis sequence

1. Double-click (Analysis Sequence).

2. Select the sequence, Design Of Experiments (Fill + Pack).

3. Click OK.

To set the material

1. Double-click (Select Material).

2. Select DuPont Engineering Polymers in the Manufactures field.

3. Select Zytel 101 NC010 as the Trade name.

158 Chapter 7

To set up the DOE

1. Double-click (Process Settings) in the study tasks list.

2. Ensure the flow process settings are set like the following:

3. Click Next.

4. Set the DOE settings as follows:

5. Click Finish.


Parameter ValueMold surface temperature 70Melt temperature 295Filling control, Injection time 1Velocity/pressure switch-over AutomaticPack/holding control %filling pressure vs. timePack/holding control profile settings 0

10 8080

Cooling time Automatic

Parameter ValueDOE Experiment type Taguchi then factorialNumber of factors 3Melt temperature Specified, Delta 20Mold temperature Specified, Delta 20Injection time Specified, Delta 75%Packing time Specified, Delta 75%Expand/compress injection profile Do not changePacking profile multiplier Specified, Delta 75%Thickness multiplier Do not change

3 The analysis will take less than an hour to run. While the analysis is running look at the results of the cap.


Reviewing the results of the cap

To review the inputs of the DOE analysis

1. Open the cap model.

2. Ensure the flow analysis settings for the cap are as follows:

3. Ensure the DOE settings for the cap are as follows:

4. Ensure the DOE Advanced options are as follows.

Parameter ValueMaterial Flint Hills Resources (Formerly Huntsman), 5824S (PP)Mold surface temperature 40ºCMelt temperature 230ºCInjection time 1.2 seconds%Volume filled 99%Pack/holding control %Filling pressure vs. time%Filling pressure vs. time 0.0

1.06.00.5

10085850

Cooling time 2.5 seconds

Parameter ValueDOE Experiment type Taguchi then factorialNumber of factors 4Melt temperature Specified, Delta 30ºCMold temperature Specified, Delta 30ºCInjection time Specified, Delta 50%Packing time Specified, Delta 75%Expand/compress injection profile Do not ChangePacking Profile Multiplier Specified, Delta 75%Thickness multiplier Do not change

Parameter ValueTaguchi ranking method Based on whole rangeFlow front temperature criterion weighting 0Shear stress criterion weighting 0Injection pressure criterion weighting 0Clamp tonnage criterion weighting 0Volumetric shrinkage criterion weighting 5Sink index criterion weighting 0

160 Chapter 7

To review the Analysis Log file

1. Click on the logs check box to open it.

2. Scroll to the Taguchi criterion ranking results.

• For each quality criterion, there is a ranking of the factors that influence the criterion. Figure 51 is an example of one of the criterion.

• When interpreting these weightings, it is important to remember what type of DOE was run, a Fill or Fill + Pack and what factors were changed and by how much. This can have a significant influence on the weightings.

• Record the dominant factor for each quality criterion in Table 38 on page 163.

• Record all the factors and ratings for Volumetric shrinkage in Table 39 on page 163.

Figure 51: Example Taguchi criterion ranking

To review the Volumetric shrinkage variation (DOE):XY Plot

1. Click on the Volumetric shrinkage variation (DOE):XY Plot.

2. Open the Properties for the result.

3. Check Packing time to make that factor the X-axis.

• Packing time is checked because this is the highest factor.

4. Click Plot Properties on the Explore Solutions Space dialog.

4.1. Set the Y range (scale) to Min 0.5 and Max 1.8, on the XY Plot Properties(2) tab.

4.2. Click OK.

5. Move the scroll bars for the three remaining factors.

6. Determine the factors required so Volumetric shrinkage variation is least sensitive to packing time.

• This occurs when the slope of the line is lowest.

6.1. Record the settings in Table 40 on page 163.

Part weight criterion weighting 1Cycle time criterion weighting 1

Parameter Value

Flow front temperature criterion weightings:-------------------------------------------------------

Factor Rank Weighting (%) Melt temperature 1 87.83700 Injection time 2 2.93008 Packing profile multiplier 3 1.98251 Mold wall temperature 4 1.38635 Packing time 5 0.07023


7. Determine the factors required so Volumetric shrinkage variation has the lowest value.

7.1. Find the conditions where any one point on the curve is lowest for any combination of conditions.

7.2. Record the settings in Table 41 on page 163.

To review the remaining XY plots

1. Review the remaining XY plots.

2. Use Explore Solution space dialog to find what conditions make the result the least sensitive to change.

To view the contour results

1. Turn off the Gate and Runner layers to leave only the Part layer on.

2. Plot the Volumetric shrinkage at ejection (DOE) result.

3. Open the properties dialog for the result.

3.1. Adjust the scroll bars.

3.2. Find a set of conditions that has a low volumetric shrinkage variation.

3.3. Find a set of conditions that has a low magnitude of volumetric shrinkage.

• Both are done visually.

3.4. Are the conditions the same?

162 Chapter 7

Worksheets

Answers for the tables are on page 164.

Table 38: Taguchi criterion rankings, highest factor

Quality Criteria Factor WeightingFlow front temperatureShear stressInjection pressureClamp tonnageVolumetric shrinkageSink IndexPart WeightCycle timeOverall quality

Table 39: Volumetric shrinkage criterion weightings

Factor Weighting

Table 40: Volumetric shrinkage, conditions least sensitive to packing time

Factor ValueMelt temperatureMold temperaturePacking profile multiplier

Table 41: Volumetric shrinkage, conditions for lowest variation

Factor ValueMelt TemperatureMold TemperaturePacking timePacking profile multiplier


AnswersTable 42: Taguchi criterion rankings, highest factor

Quality Criteria Factor WeightingFlow front temperature Melt temperature ~89%Shear stress Packing profile multiplier ~90%Injection pressure Packing profile multiplier ~61%Clamp tonnage Packing profile multiplier ~89%Volumetric shrinkage Packing time ~83%Sink Index Packing time ~52%Part Weight Packing time ~36%Cycle time Packing time ~93%Overall quality Packing time ~89%

Table 43: Volumetric shrinkage criterion weightings

Factor WeightingPacking time ~83%Packing profile multiplier ~15%Melt temperature ~1%Mold wall temperature >1%Injection time >0.2%

Table 44: Volumetric shrinkage, conditions least sensitive to packing time

Factor ValueMelt temperature 260ºCMold temperature 70Packing profile multiplier ~1.2% to 1.75%

Table 45: Volumetric shrinkage, conditions for lowest variation

Factor ValueMelt Temperature 200ºCMold Temperature 70ºCPacking time 1.9 Sec.Packing profile multiplier ~1

164 Chapter 7

Competency check - DOE

1. What does the Taguchi DOE experiment type provide you?

2. What does the Factorial DOE experiment type provide you?

3. What is the advantage of running a Taguchi then factorial DOE experiment type?

4. Will the DOE analysis show the optimum molding conditions for the part as a single result?


166 Chapter 7

Evaluation Sheet - DOE

1. What does the Taguchi DOE experiment type provide you?

• The Taguchi performs a screening analysis which allows the user to determine which variables have the major impact on the part.

2. What does the Factorial DOE experiment type provide you?

• The Factorial analysis performs a full factorial analysis and gives the user information of the kind and level of interaction between the variables.

3. What is the advantage of running a Taguchi then factorial DOE experiment type?

• The program will run first a Taguchi analysis to determine the primary factors to be used in the factorial analysis making more efficient the analysis time and results.

4. Will the DOE analysis show the optimum molding conditions for the part as a single result?

• You need to look very carefully at the DOE results to be able to draw conclusions from it. The DOE analysis will not show the optimum molding conditions for a part. The DOE tool will enable you to draw conclusions about which factor to control and by how much so that the required quality is achieved.


168 Chapter 7

CHAPTER 8

Projects

Aim

This chapter contains parts of many different types with many problems to be solved. One or more of these can be worked on.

Why do it

With many different types of problems, from translation issues to difficult to solve filling problems, it will provide a variety of problems to investigate and solve.

Overview

This chapter applies to all mesh types.

The projects include:

• Finding a gate location on a boot part on page 167.

• Optimize the 8-cavity tool for cap on page 168.

• Determine gate location and molding conditions for a change tray on page 170.

• Find the gate location and size the runner system for a cover on page 172.

• Determine gate locations for a chest of drawers on page 174.

• Finding a gate location for a dustpan on page 175.

• Determine type of tool and gate location for the Grab-it model on page 176.

• Determine the gate location for a light holder on page 177.

• Determine the gate location for the paper holder model to minimize weld lines on page 178.

• Find a gate location and process settings for the phone housing model on page 179.

• Find a gate location and size the manifold for the reel model on page 180.

• Optimize a 4-cavity tool for the Snap Cover model on page 182.

• Find gate locations and balance runners for the door panel model on page 184.

Projects 169

170 Chapter 8

Finding a gate location on a boot part

Determine the gate location and processing conditions for a two-cavity boot tool.

A primary concern is air traps that would prevent the boot from having a tight seal.

Once the gate location and processing conditions are found, determine a proposed cavity layout and size the runner system.

1. Translate the Boot IGES model.

Reduce the aspect ratio to below 6:1.

Remove all other mesh errors.

Make the orientation consistent.

2. Determine the gate location.

The mold is a two-plate tool with a layout of your recommendation.

Use tunnel gates.

3. Use the TPU Texin 270.

Make material change recommendation if necessary.

Must be a Texin grade.

4. Determine optimum process settings.

5. Optimize part filling.

No air traps that can’t be vented.

Shear stress below material limit.

Minimum number of weld lines.

Balanced filling pattern.

6. Layout runner system for a 2 cavity tool.

7. Size tunnel gate.

Maximum shear rate below 25,000 1/sec.

Minimum included angle 10º.

8. Size runners to minimize runner volume.

9. Sprue located in the center of the tool.

Recommend sprue orifice diameter.

Sprue included angle 2.38º.

171

Optimize the 8-cavity tool for cap

1. Optimize the molding conditions and size the feed system for the 8-cavity cap tool.

2. Translate the Cap IGES model.

Reduce the aspect ratio to a reasonable number.



3. Use PP, Flint Hille Resources P4-011.



6. Layout runner system for an 8-cavity tool.

Use the sketch on the following page.



Recommend runner sizes.

Size the drops if necessary.

Determine the gate orifice size.

Use as starting point the preliminary sizes.

172 Chapter 8

3 All dimensions are in millimeters.

173

Determine gate location and molding conditions for a change tray

1. Use only a fill + pack analysis, the information given and the use of design principles, determine the gate location and processing conditions that will keep the flatness of this part to a minimum.

2. Translate the Change_Tray IGES model.

Reduce the aspect ratio to a reasonable number.



Ensure the minimum thickness is at least 1.5mm and the maximum thickness is under 2.0mm.


The mold is a 2-Plate tool with a proposed cavity layout. The layout can change in necessary. See the layout on the next page.

Use edge gates.

4. Use, LG Chemical, HIPS 60HR.

Make material change recommendation if necessary.

Must be a HIPS grade.

5. Determine optimum processing conditions.



Shear stress below the material limit.

Uniform temperature distribution.

7. Layout runner system for a 4 cavity tool.

8. Size edge gate.

9. Maximum shear rate below 20,000 1/sec.

Minimum thickness 1.0 mm (0.040”).

Width less than 6.4 mm (1/4”).

Size runners to minimize runner volume.



10. Optimize volumetric shrinkage to minimize the variation of the shrinkage.

174 Chapter 8


175

Find the gate location and size the runner system for a cover

1. Locate the gate on this part that will help minimize warpage.

The material is a 30% Glass filled Nylon. Fiber alignment will dominate warpage.

The proposed tool layout is provided.

The cavity layout can change.

Edge gates can be used.

2. Translate the Cover IGES model.


The 4 posts on the under side of the part are translated in as triangles. They need to be modeled as beams. Use the tool Modeling Simplify Model.



3. Use PA66, Zytel DMX 61G30H BK407.

4. Find the gate location.





7. Layout the runner system.

Sprue length is 90.49 mm.

8. Size the following:

Sprue orifice.

Runners.

Edge gates.

9. Make sure the gate shear rate is below 25,000 1/sec.

10. Ensure the volumetric shrinkage between the cavities is uniform.

176 Chapter 8


177

Determine gate locations for a chest of drawers

1. Determine if the chest of drawers part can be produced with edge gates. Minimize the weld lines on the part, there can NOT be weld lines down the center axis of the part.

2. Translate the Drawer IGES model.




3. Use HIPS, BASF Polystyrol 456 F.

4. Find gate location.




Uniform pressure distribution.

No weld lines down the center axis of the part.

Only a small variation in temperature.

178 Chapter 8

Finding a gate location for a dustpan

1. Find the gate location and size a hot sprue bushing that will be on the part. The 2-plate tool will be a single cavity. Place the gate on the part to have a balanced filling and packing. Size the gate orifice to keep shear to a minimum.

2. Translate the Dustpan IGES model.




3. Use PP, Daelim Industrial Co Ltd HD2002.







Move the gate as necessary to achieve the balanced pattern.

7. Model the hot sprue per the sketch.

Size the bore diameter and gate orifice as necessary.

Keep the shear rate below 40,000 1/sec.

8. Ensure volumetric shrinkage is uniform.


179

Determine type of tool and gate location for the Grab-it model

1. Determine the type of tool that will need to be constructed for this part. The options include a 2-plate cold runner tool, a 3-plate tool, or a 2-plate tool with a hot runner. Decide on the gate location then lay out a proposed 4-cavity layout with the proposed runner system.

2. Translate the Grabit IGES model.

Reduce the aspect ratio to below 15.



3. Use LDPE, Basell Polyolefins Lupolen 2420 K.







Move the gate as necessary to achieve the balanced filling pattern.

Consider both edge gates and gates on the surface of the part.

7. Design the feed system for the 4-cavity tool based on the gate location chosen.

8. Size the gates to keep the shear rate below 30,000 1/sec.

180 Chapter 8

Determine the gate location for a light holder

1. Find a gate location that will minimize the weld lines around the opening for the light. Only edge type gates can be used. Design a gate and runner system for a 1-cavity prototype tool.

2. Translate the Light_holder IGES model.




3. Use PA6, BASF, Ultramid 8333GHI.





No weld lines around the opening for the light.



7. Design the feed system for a 1-cavity tool based on the gate location chosen.

8. Size the gates to keep the shear rate below 20,000 1/sec.

181

Determine the gate location for the paper holder model to minimize weld lines

1. Find a gate location that will minimize the weld lines on the large curved sides of the paper holder. Modify the wall thickness if necessary. The tool will be a single cavity 2-plate tool.

2. Translate the Paper_holder IGES model.


Ensure the maximum thickness is <5.6 mm and >1.9 mm.



Use SAN, Dow Chemical USA, Tyril 100 C.

Find gate location.



5. Balanced filling pattern.

6. No weld lines on the large curved sides.


182 Chapter 8

Find a gate location and process settings for the phone housing model

1. The phone will be molded with in-mold labels. High shear stress and weld lines reduce the adhesion of the labels to the part. Determine a gate location, and processing conditions that minimize these problems.

2. Translate the Phone IGES model.





3. Use PC+ABS, Bayblend KU 2-1468.





Minimize weld lines that meet head on.


183

Find a gate location and size the manifold for the reel model

1. Find a gate location and size the manifold for a 2-cavity reel tool. The gate location should produce minimal stress in the hub of the part.

2. Translate the Reel IGES model.





3. Use PC, Lexan SP7606.





Shear stress below the material limit in the hub of the part.

7. Layout and size the hot runner system.

The drop length is 88.9 mm.

Determine the gate diameter.

Size the drop and manifold diameters.

The sprue length is 25 mm.

184 Chapter 8


185

Optimize a 4-cavity tool for the Snap Cover model

1. Determine the gate location and size the runner system for a 4-cavity snap cover tool. A proposed cavity layout is provided.

2. Translate the Snap_Cover IGES model.

Reduce the aspect ratio to under 6:1.




The mold is a 2-plate tool with a fixed cavity layout. (See sketch on following page).

Use tunnel gates.

4. Use ABS, Lustran ABS 248.






7. Layout runner system based on cavity layout and gate location.

8. Size tunnel gate.

Maximum shear rate below 30,000 1/sec.

Minimum included angle 10º.


Sprue located in center of tool.

Sprue orifice diameter 5.56 mm (7/32 inches).


186 Chapter 8

187

Find gate locations and balance runners for the door panel model

1. Determine the gate locations for the door panel. Only edge gates can be used. Size the hot and cold runners necessary to produce the single cavity tool. The center of the tool will be at the clamp force centroid.

2. Translate the Door_Panel IGES model.

Reduce the aspect ratio to under 20:1.



3. Determine the gate location(s).

The mold is a single cavity 2-Plate tool.

Only edge gates can be used.

A hot runner will be designed to deliver material into a cold runner system feeding the gates.

4. Use ABS, Kralastic SXB-367.






Clamp force limit 2500 metric tons, limit filling to 2000 tons.

7. Layout runner system.

Based on gate location(s).

Sprue in centroid of clamp force.

Size hot manifold, drop(s) cold runners and gates as necessary.

Drop length 350 mm long.

Sprue length 25 mm long.

8. Optimize volumetric shrinkage within clamp tonnage limit.

188 Chapter 8

What You’ve Learned

This chapter demonstrated many problems which may be investigated using Moldflow Plastics Insight.

The tasks which were performed included:

• Finding a gate location.

• Optimizing multi-cavity tools.

• Determining process settings.

• Sizing a cold runner system.

• Balancing a runner system.

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190 Chapter 8

IndexNumerics2D Slice zone plot ............................................... 17

AAdd, studies .......................................................... 19Analysis Log ......................................................... 35

BBalance pressure .................................................. 22Balance runners ................................................... 22

CClamp force ....................................................69, 87Clamp tonnage ..................................................... 29Constant pressure time .................................74, 92Create a database ................................................... 3

DDatabase

Copy ................................................................. 4Create ............................................................... 3

Decay time .....................................................74, 92Determine initial packing time ....................70, 88Determining initial packing pressure .........69, 87DOE

Advanced options ...................................... 160Contour results .......................................... 162Quality criteria ............................................ 163Quality criterion ......................................... 161XY plots ...................................................... 161

EEdit a material property ....................................... 5

FFeasible molding window .................................. 16Flow rate ............................................................... 21Frozen layer fraction ........................................... 75

MMaximum machine injection pressure ............. 16Molding conditions .......................................14, 34Molding window

Process settings ............................................ 16

OOptimizing a packing profile .......................68, 86

PPacking

Pressure .................................................. 69, 87Pressure, determine ............................... 75, 94Profile, create ......................................... 76, 95Time ........................................................ 70, 88

Preferred molding window ................................16Pressure

XY plot .............................................37, 73, 92Process settings

Molding window ..........................................16Process Settings Wizard ......................................23

SSave Study .............................................................16

TTarget pressure .....................................................22Transition point ............................................ 74, 92

Uudb ...........................................................................3Using a personal database ....................................5

VVolume change ....................................................23Volumetric shrinkage ................................... 72, 90

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Documents

Autodesk Moldflow Insight 2010 Std2 Practice